Anodizing and dyeing aluminum without battery acid...

10/16/2011

There is now an updated video on YouTube here. I did not show the dyeing step and it should be mentioned that after being in the dye, the anodized piece should be placed in boiling water to seal in the color. 25 September 2015.

Video and write up below:
The anodizing and dying of aluminum parts at home has long been a popular project for many people. But the use of battery acid, typically (29% to 32% sulfuric acid) causes concern and reluctance, and prohibits others from even trying to anodize aluminum at home. It can be difficult to store, dangerous to skin and clothing, and in general, not fun to work with. OSHA lists it as corrosive. This project provides an alternative to the use of liquid sulfuric acid and uses instead, a granular pool chemical that is easy to find, mix, store, and work with. OSHA lists this chemical as only an irritant with no shipping restrictions. Disposal is straightforward using baking soda to neutralize and the results are comparable to those obtained with the use of the sulfuric acid method. The alternative chemical is sodium bisulfate (NaHSO4) the sodium salt of sulfuric acid but in weaker form. It is also known as sodium hydrogen sulfate and is used to lower the ph in home swimming pools. As in the use of any chemicals, care and caution are in order. The following video is a project overview followed by a step- by- step write-up:

Aluminum and some other metals have a naturally occurring barrier coating that comes about because of a reaction with the oxygen in air. In the case of aluminum, that barrier is aluminum oxide, Al2O3. All processed aluminum has this coating. But, it has long been known that by using an electrolytic process the metal can have additional protection.
In general there are two types of barrier coatings. The first is a thin, hard coating that increases the hardness and insulation properties. The second is a porous cellular structure that allows a dye to fill in the cells and provides a decorative and protective coating. This is the structure that is needed for this project. After the dye has filled the anodized cells with color, the piece is placed in boiling water for 20 to 30 minutes to seal the dye in completely.
Required materials:
·      Sodium Bisulfate, NaHSO4, also called Sodium Hydrogen Sulfate. The pool additive used is Aqua Chem balance+protects- pH down. I found this and similar products to lower pH in pools at both a garden center and the hardware store. Look for the chemical name and at least 90% active ingredient.
·       Sodium Hydroxide. (Optional) NaOH also called drain cleaner or lye, available at all hardware stores.
·      RIT liquid dye. I have used several colors but only in the liquid concentrated form. The dry packets may work but I have not tried them. Available in grocery, drug, and hardware stores.
·      Battery or source of DC current. A 1.5 volt D cell can be used. I used a rechargeable 6 volt battery but a wall wart will also work well. This project likes relatively low voltage and current less than 400ma for these small parts. Slow anodizing seems to work best. Voltage and current guidelines for larger pieces will be listed in the closing comments.
·      Aluminum or Lead for the cathode. (Negative Battery lead). Both are essentially inert in this chemical. Some aluminum will be deposited at the cathode but it can be removed easily.
·      Aluminum metal to anodize.
Procedure:
Make a 2% (dilute) solution of sodium hydroxide (Drain Cleaner, NaOH) if you desire an etched surface prior to anodizing. 4 grams of NaOH in 196 ml of tap water. Or, ¾ cup water to 1 teaspoon NaOH. Mix with plastic or wood tongue depressor. Distilled water is best if you have some. This will be used to clean and prepare the aluminum surface. This measurement is not critical!
Make a 20 % solution of Sodium Bisulfate, (pool Ph down), also called sodium hydrogen sulfate. 40 grams of sodium bisulfate in 160 ml of tap water. Or, 2 and ½ Tablespoons sodium bisulfate to 2/3 cup water. Mix well with plastic or tongue depressor. Ph will be between 1 and 2. This can be increased up to 30% if needed.
Make the RIT dye solution. General guideline is 5 ml liquid dye with color of choice to 250 ml of water. Or, ½ Tablespoon dye to 1 cup water. This measurement is not critical and the concentration can be increased based on results.
Process:
Prepare the aluminum for anodizing by cleaning thoroughly. I typically use fine steel wool to remove the surface contaminants and reduce imperfections. This is followed by a wash with a Scotchbrite pad and dish detergent. Rinse well and either proceed to the sodium hydroxide etch for 2 to 3 minutes and rinse again, or go directly to the anodizing solution. The etch step provides some “bite” for the solution and allows for slightly larger cell size. Aluminum alloys are highly variable so experiments with scrap pieces are encouraged.
Attach the negative battery lead to the cathode which should be at least as large as the piece being anodized. Attach the positive lead to the piece to be anodized. Picture at end of post.
Small bubbles of hydrogen will be seen at the cathode. The time required for anodizing depends on alloy composition, current draw, solution temperature, and solution concentration. Start with 30 to 60 minutes. A good indicator is that the piece will have a slightly yellow tinge as the index of refraction changes with cell growth. Rinse the completed part in cold water and place in the dye bath at room temperature. Allow about 60 minutes and rinse the part in cold water. If the color density is low, place it back in the dye bath for a longer period.
When the color is correct, place the piece in boiling water for 20 to 30 minutes to seal in the dye. If a further protective coating is desired a clear coat of spray acrylic can be added to highlight the color.
For reference purpose, here is the formula that was used to anodize the control with the battery acid method. 50 ml of battery acid (30% H2SO4) , to 150 ml tap water.
Closing thoughts and link:
The current required for anodizing in general is very much a variable, but a guideline is 2.8 to 10 amps for one square foot of aluminum. This process is very open to experiment and optimization.
Two ideas that I have not tried yet is to raise the temperature of the anodizing solution, and the thought that it would be helpful to find a material to resist anodizing solution attack. I have tried Sharpie and Krylon clear acrylic spray with some fair results. Any ideas and comments would be appreciated.
The link for the Encyclopedia of Electrochemistry is here:

Thanks to all for the comments and the suggestions are always welcomed. If someone comes up with a good working example of a resist using this process, send a note via the comments and I will contact you and post the results as a guest post. For all that caught the use of "dying" instead of "dyeing" you are absolutely correct. My bad use of the English language. Apologies to all!

553 Comments

Lynette

11/5/2012 03:05:55 pm

Thanks, Ken - I was looking for a safe way for my science students to make Christmas decorations. Now I have it - anodised stars,

Lynette

Michael Ward Jr

2/23/2020 09:13:15 am

Ken question about the power supply is there one you reccomend ?

Jeremy

1/28/2013 03:52:01 pm

I tried this method tonight and there were tons of hydrogen bubbles coming off of the anode and cathode. My part is currently in the dye and appears to be working, but I want to make sure the amount of bubbles was ok. I used a screw to secure the anode lead to my part. The mixture ate away at the screw. What is the best way to attach the anode lead to the part? I want to make sure all areas of the part are anodized. In other words, I need to completely submerge it.

Ken

1/29/2013 12:59:37 am

Hi Jeremy, One thing that I have done is to pick up some aluminum wire and use it to form a "paper clip" like connector. That way, you can submerge the item and not have it eaten up by the acid. If the item is tpp thick, use the wire to make some type of clip. There should be a large amount of hydrogen bubbles that are very small. Also, rotate the clip to make sure that all of the item is anodized. Thanks for the comment, Ken.

Ruslan Alsaaid link

12/14/2014 02:52:30 am

Dear Ken

I have been FAILING miserably in Anodizing for a week now.
Have been trying all kinds of Chemicals.

First i have been Degreasing in Sodium Hydroxide
Than I put in Nitric Acid, after that Anodizing with 0.8 amp 20Sq/inch
tried with 1.5 amp and many different voltages. all connected directly to anode as aluminum piece. Cathodes are also aluminum sheets.
Tried with Different Dyes for clothing. None of them stick on the Aluminium piece after Anodising. I have no idea. Does it even anodise or not. Please could you help me.

ian

5/14/2014 12:01:34 pm

You probably used a steel screw which wont hold up to h2so4- use aluminum screws or hardware and they won't corrode

Mick

6/8/2017 12:13:27 pm

Instead of aluminum for the cathode, use a lead sheet. The aluminum cathode will anodize and reduce the current

Jeremy

1/29/2013 09:37:05 am

Ken, thanks for the reply. The first go round appeared to be taking in the dye, but ended up not taking so well. I got some aluminum wire earlier today and am trying it now. On the first try, I couldn't even see the part. There were too many bubbles. The battery I was using got warm to the touch, but this time it is still room temp. So, I think the fastener I was using the first time either contaminated the mixture or was being attacked by it. I used a screw and it had been eaten away where it broke the surface of the mix. Hopefully this time it will work better. I am getting tiny bubbles just off of the cathode and can clearly see the part. I'll update here when it's done. Thanks for your help!

Jeremy

2/1/2013 12:18:31 am

Well, I did get the part to anodize, but it still didn't take as well as I'd like. I'm trying again today with distilled water instead of tap water. The part is currently in the dye. I'm trying to dye the part black. Have you had any issues with this process using the black dye? I haven't tried any other color.

Ken

2/1/2013 01:09:15 am

Jeremy, black is the most difficult color to dye aluminum. But, success is possible. Definitely use distilled water, try increasing the voltage as this may change the pore size. Remember, aluminum has a protective oxide that has to be attacked by the anodizing process to form the pores that will accept the dye. It is a variable process that may require some experiments to determine what is happening. Longer anodizing times, higher temperature, different grade of aluminum, and patience are helpful. There is also a company called Caswell that sells dyes that may be better but I have not used them at all. Something else that just occurred to me is that pre-etching with the Sodium Hydroxide may be useful if it is used and the time of etching increased. Keep us informed, Ken.

Schuyler

12/31/2016 02:20:54 am

The color you're seeing is the result of a phenomenon most apprentice auto body painters find out the hard way. it typically happens with silver flake and black. I'm guessing your etch was too strong.

Jeremy

2/1/2013 09:25:54 pm

Well, I'm not sure what happened this time around, but my part is actually a gold color and not black or purple at all. Weird. I'm using a rechargeable 7.2V 1800mAh nimh battery for the power source. My part is approximately 40mm x 50mm and 1/8" thick. I used distilled water this time and anodized for around 1-1/2 hours. Rinsed and then into the dye for about 1/2 hour or so. Then, ibto boiling water. I think one problem I'm having is my cathode is a piece aluminum flat bar I got from Lowe's. I have done a little research and found that this aluminum is between a 2000 series and 5000 series. I'm thinking this lower grade is hindering my process as well? I anodized at room temp, rinsed room temp, dyed in heated solution (not sure what temp) and then sealed in boiling water. What are your thoughts?

Ken

2/2/2013 01:15:57 am

I am a little perplexed by your results. Are you saying that with prior conditions you were successful and with these conditions it was a failure? While it is difficult to diagnose from a distance, the condition you are describing is related to pore size. It may be due to the grade of aluminum, but I am uncertain. I used 6061 which is available in most hardware stores. A quick test is to use a piece of lead as the cathode. It is available as lead flashing at lowes. Fishing sinkers used to be lead but they are now made of bismuth. There are also some solders that are lead. Anodizing is an art and not always a science but we will figure it out. A quick thought- Is the part you are anodizing really clean and well prepared. Is it etched in NaOH? Keep on keepin on. Ken

Jeremy

2/2/2013 09:55:28 pm

Ken,
I am attaching a photo of my anodizing adventure. From left to right: first one was done with tap water and the 7.4V 1800mAh battery and black dye. Anodizing time of 1 to 1.5 hours. It did anodize, but the color is light and didn't take completely. The second was done with distilled water and the same battery. Anodizing time of about 2 hours. It actually came out a goldish color. On this attempt, I did heat the dye (have seen many videos of people doing this), but I think that was a mistake because the heat may be sealing at the same time. The third was started with the same battery, but changed to a 15V 500mA power supply half way through the anodizing process. Time of 2 hours total. Etching was done as well. Dyed in red this time (heated dye) and the part had previously been polished. Also distilled water on this one. The last one was done with the 15V 500mA power supply for the entire duration. Distilled water and also etched. 2 hours for anodizing time. Also, added a little more sodium bisulfate on this one. Dyed in red at room temp.

All dying times were at least an hour. The first three parts are 6061 T6 aluminum. The last is a piece of the flat stock I got from Lowe's. I used the flat stock as the cathode on all attempts. I think I've got it now. I don't think I will heat the dye anymore. I will most likely get the lead as you suggested. That should make a better cathode, correct? Also, all parts were suspended in the anodizing mixture with aluminum wire, except for the last. I clipped the positive lead directly to that one. Anyway, check out the pic and please let me know what you think. I need to get this process down, because I need to anodize larger parts soon. Thanks for your help.

http://i1032.photobucket.com/albums/a409/ponie1992/2013-02-03_08-12-52_128_zps5cd4e050.jpg

Ken

2/3/2013 01:17:53 am

Well done Jeremy- The results are interesting and except for the gold one, expected. Several thoughts. I would not heat the dye solution as your observation about the closing of the pores is right. I did some research on RIT versus Caswell dye and it seems that Rit should be fine even though it is a dye for cloth. I would also suggest that you check current draw if you have a multimeter. It would give you a guideline as you increase the size of the parts you want to do. Additionally, if you have not read the link in my writeup to the Encyclopedia of Electricity, it may be worthwhile to look at the conditions for the pore size. Also, I am including a link to a home process that may be of interest. He used sulfuric acid but the chemistry remains the same. As mentioned, black is a tough color to use but perseverance will prevail. Ken.
http://www.thefintels.com/aer/homealuminumanodizing.htm

Jeremy

2/3/2013 11:37:32 am

Ken,
Thanks for the link. Very interesting. I'll make sure to check out your writeup as well. Oh, and thanks for this blog. Without it, I would be using battery acid and I wanted a "safer" method so to speak. I'll keep in touch and let you know how I come out with larger parts.

Jim

2/14/2013 12:52:21 am

Ken,
Thanks for the info. I wish to anodize some raw aluminum spoke nipples and was wondering if aluminum wire run through the nipples would give a decent finish. Quality of finish is not a huge concern but more so coverage, as a lot of the nipple is covered by the rim and the round shape should hide any imperfections. Thoughts ?

Ken

2/14/2013 03:23:51 am

Jim,
I assume that you have chosen aluminum over brass for a reason so I will address this issue. All aluminum, nipples include, can be anodized but results vary as to the composition of the aluminum. It seems as if your question relates to the electrical connection between the wire and the ID of the nipple. It really does not require extensive contact for anodization so a quick test should provide the answer. If I have not understood the question correctly, please let me know. Ken.

david barr link

3/3/2013 03:20:14 am

Hi Ken My company New Orleans Mint stopped anodizing 15 years ago. We mint mardi gras coins and would like to find a new way to color our coins in house without the epa problems , shipping costs and delays we struggle with every year.
Are you available to consult with us and set up a new anodizing plant. We anodized well over a million coins.
thanks , david

Ken

3/3/2013 08:05:29 am

Hi David,
There are some possibilities for collaboration but there are more questions to answer first. What is the metal you want to use, What are your concerns with the EPA specifically, Do you presently have an anodizing setup, do you want to do everything in one location? It would help if you contact me via email with clearer direction and a link to your site. [email protected]. Thanks for the comment, Ken.

Dave H. (the other one)

3/4/2013 08:15:42 pm

Hi Ken, useful info!
Re cathode materials, I've had good results using carbon rods, I use the copper-coated ones sold as arc brazing/gouging rods and strip all but an inch of the copper with ferric chloride to leave a solderable connection, works very well for small-scale anodizing.
Inkjet printer ink can give good results, but some experimentation is required, I found black ink gives a beautiful bronze colour!

One thing worth emphasis is that the finish that goes into the tank is what comes out of the tank, anodizing *will not* hide imperfections! A bad job can be stripped with a short dip in caustic soda (lye) solution, which will also strip the existing oxide film on raw aluminium prior to anodizing - strip and rinse with distilled water, ans store under water until it goes in the tank to reduce oxidisation for best results...

have fun

David F

3/17/2013 05:00:19 pm

So i have some clear anodized aluminum at home, it misumi 2040 aluminum extrusion to be exact. what im wondering is, if i can just dye it, since its already been anodized. based on what ive read, i think it may be possible as long as there is no clear cote on it. thanks, and nice work.

Ken

3/18/2013 02:06:02 am

Great question David, and the answer is somewhat dependent on several factors. Anodizing is a passivation process which makes the surface passive to the environment. If it was previously anodized, but not designed to be dyed, the cell structure will be small and any dye added now would be poorly accepted. Also, aluminum will naturally oxidize over time and the cells will become inert (almost), thus making the dyeing process impossible. My best guess is that success is unlikely but if I were you, I would try it anyway. I have been wrong before but logic tells me that the task is difficult. Even if it accepts color, the protection will be minimal. If you have a piece that you can try it on, let us know what happens. Ken.

Kelly W

4/13/2013 02:08:30 am

Hi Ken, I would like to thank you for a great article and have a question.
Do you know what the specific gravity of the ideal Sodium Bisulfate solution would be? That would make it easier to set up different sized baths. Also, could you put die into the anodizing solution so that it is absorbed during the process making a black more intense?
Thanks and keep up the great work!
Kelly

Ken

4/13/2013 09:28:25 am

Hi Kelly,
The specific gravity of a 20% solution sodium bisulfate is close to 1.150, which is lower than battery acid at 1.265 at STP. However, as you probably know, the SG is a moving target with temperature change and rate of electrolyte loss. I would be reluctant to trust the SG and would stick to whatever the best concentration of sodium bisulfate you find the best for your application and type of aluminum. My suggestions are simply that and you can change the concentrations and temperatures as well as current draw/voltage. I have not tried to make the dye a one-step process but I am guessing that since the cells need to be open before the dye can begin to color the aluminum, that the dye will interfere with the color absorption. But, it would be helpful to know if it can be done so give it a try and let me know. You may be onto a really great idea. But, in general for deeper blacks I have suggested the Caswell professional dye but have not used it myself. Thanks for the comment and stay in touch! Ken.

Kelly W

4/13/2013 02:53:23 pm

Ken, thank you for your reply and comments. I have ordered some of the Caswell black but it hasn't arrived yet. I will try some experiments with dye solution and electrolyte but agree that it will probably not work. No harm in trying though. I will also post my results from the using the Caswell product.

Cheers,
Kelly

Kelly Wilson

4/20/2013 12:23:46 am

Hi Ken, as previously promised, here are the results of using the Caswell black product. Following all the guidelines as posted by you above and using the 720 rule the results have been awesome. The black is very deep and rich and coverage is excellent. The color's lack of transparency is also impressive. For anyone wanting to do black, I would highly recommend this product. It is quite expensive though at around $40 for 2.7 oz which is enough to treat 2 gallons of water.
The only additional comment that I would like to put forth is that I added an extra cleaning step before the anodize bath and wiped the piece down with 99.9% Isopropyl alcohol which actually revealed that soap and water doesn't remove everything.

Overall for my second attempt at anodizing, I am astounded by the results. Thank you Ken for creating and maintaining this page as I have found it to be inspirational.

Cheers,
Kelly

Kelly Wilson

4/20/2013 12:31:03 am

As a footnote to the above, I forgot to mention that I heated the dye bath to a temperature of 140 degrees F and maintained that for the whole 30 minutes that the part was submerged.
This heating of the Caswell dye seems to be an important part of the process.

Cheers,
Kelly

Ken

4/20/2013 02:42:23 am

Hi Kelly,
Thank you for adding to the knowledge base of this process and your efforts are greatly appreciated. I have found that anodizing is sometimes more of an art than a science. But, you have shown again that perseverance and careful thought can provide the desired outcome. As I have mentioned before, I consider failure a good thing as it provides data points and suggests changes. Congrats on a great dialog and valuable information. If you have ideas for other projects please let me know and we can consider a guest post. [email protected]. Ken.

GeoB

8/2/2013 12:54:20 pm

If I may... be patient with me, my chemistry days are far behind me. I was reading about a great way to remove rust from ferrous material. IIRC you use the same sodium-bisulfate solution to immerse the subject object. Don't recall the details, correct me if I'm wrong, but I think the part to be cleaned is the anode (the negative connection to your DC source). Don't think the cathode material is important really.

Kelly Wilson

4/25/2013 11:32:19 am

Hi Ken,
I was wondering if you could offer some advise.

My anodizing seems be working just fine doing brushed aluminum pieces by when I try to do a smoother finish with finer grit 600 - 1500 wet process or rub with superfine steel wool I seem to have issues with the outside 1/8th inch perimeter of my sample 1 x 3 inch flat pieces. Specifically it won't take the die as if the edge layer is too thin or non existent. I have tried various cleaning and etch steps but the results are consistent.
I am anodizing using Sodium Bi-Sulfate 20% solution with the 720 rule @ 12 amps per square foot which by my calculation means running 250ma for 60 minutes. Then rinse with room temp distilled water and then into the dye solution @ 140 degrees.
I can tell almost instantly that it is not going to take around the edges.

Any suggestions ?

Thanks,
Kelly

Ken

4/26/2013 08:47:36 am

Hi Kelly,
I have several thoughts and an educated guess about the problem. One of the biggest problems resulting in partial anodizing is with metal contamination. Emery wet/dry frequently has Fe (Iron) or other metal content. Similarly, steel wool has Fe as well. When we abrade the piece we tend to press harder on the edges causing micro metal contamination. I would first confirm that the aluminum is clear of any contamination by etching mildly in the sodium hydroxide solution and nothing else to see if the anodizing is uniform. If it is uniform I would not abrade it but would use a Dremel with a buffing wheel and polish it. You could also use a cheap battery powered nail buffer. Let me know how the work progresses as I may have more information. Ken.

David

4/30/2013 05:51:44 am

Ken,

Thanks for the great article. I have a Quadrajet carburetor I just want to protect from the under-hood environment and keep it looking nice. I was thinking I could polish it with a Dremel and then anodize it without any dye. Would that work to get me a bright natural finish?

Ken

4/30/2013 09:51:11 am

Hi David,
My best guess is that the carburetor is an alloy of aluminum and if you use the project as suggested the result will be a slight yellow tinge. The same would hold true with sulfuric acid anodizing as well. When polished, the surface will form an oxide layer on its own over time. It could theoretically be polished and then coated with a sealer which I would recommend. There are a multitude of sealers available and can be found with a search for "aluminum sealers". Sorry for the lack of applicability of my project for your needs. Ken.

Jason B

5/22/2013 12:36:52 pm

Hi Ken,

I am going to try this method this evening--thanks for sharing this info. I am wondering a few things: the current you use is very low by typical standards; have you found that there is an upper boundary at which results diminish? Is there a formula for estimating the ideal current for this process? I was also wondering how many parts can be done in the NaHSO4 solution before it becomes too weak or too contaminated? Is it the type of thing where you can mix up a fairly large bucket full and use many times? Another thought occurred to me: can I use an aluminium pot as both the container and the cathode? This would provide a large surface area but care would be necessary to avoid short circuits, of course.

Anyway, thanks again for sharing this! I really lucked out finding your page because I was wishing for a less-toxic method to try this at home, and this seems ideal.

Cheers,

Jason B
Wisconsin

Ken

5/23/2013 01:43:12 am

Hi Jason,
There are several current guidelines but it really depends on the alloy being used. The general rule is from 2.8 to 10 amps per square foot of aluminum. But, if you check the last link in the write-up the cell size varies proportionally with current so use a test piece to get the best result. The best way to test the quality of the solution depletion would be by using pH paper. Test the pH at the start and test periodically and watch for increasing pH. It should remain in the range of 1 and 5. But, it will still work. The use of an aluminum utensil as the cathode will work if you can avoid anode contact. Best of luck! Ken.

Jason B

5/23/2013 03:37:18 am

Hi Ken,

Thanks for the reply. I noticed that in your above calculation for the % solution of the NaHSO4 you say to add 40g into 160 =ml of water for a 20% solution. 40/160 = .25 Wouldn't this yield a 25% solution? Also, is tap water OK for the final sealing step, or is it still best to use distilled?

Thanks,

Jason B

Ken

5/24/2013 02:38:13 am

Hi Jason B.
For mass percentage solution it is 40/200 (the total solution) = 0.2 X 100 = 20%. Tap water is fine for the sealing step as it is simply closing the pores with the included color. Thanks for the comment. Ken.

Jason B

5/24/2013 04:22:44 am

I just wanted to add that my first attempt turned out great! I did end up using a lot more current than you use, here. I found best results at 18v and about 1 amp for a part about the size of a golf ball. I am not sure why this is the case, but I have a wide range available, so I just looked for what worked best. At the lower voltages I was not getting enough current to flow. Could this be a sign that I need the electrolyte to be stronger?

Thanks,

Jason

Ken

5/25/2013 01:53:14 am

Nice work! The current does seem high but I have learned that this process is as much an art as a science. The variables can drive you crazy as we typically like to change only one at a time. After I have used this process I simply did as you; do what works! I would not assume that the electrolyte is too weak as long as the pH is still acidic. If you have not read the last link in the post to the Encyclopedia of Electrochemistry it would be good to get an understanding of all of the variables to the pore size. Ken.

ammad

6/16/2013 06:37:56 pm

hy ken' I tried this by sulfuric acid and there was many bubbles occurring from anode .
plz tell me what I have to do

Ken

6/17/2013 08:49:54 am

Ammad,
Are you certain that the anode is the plus voltage? Thee may be some bubbles at the anode but the cathode should have a lot hydrogen. Ken.

ammad

6/18/2013 11:18:24 pm

thanks for reply ken .
recently I used lead on cathod(negative side) and bubbles come from both sides but on cathod they are less.
I used 32% sulfuric acid.
now how much volt I have to give to 6 inches long aluminium pipe?

Ken

6/19/2013 01:53:00 am

Ammad,
The more critical measure would be the current. Consider 1.5 amps needed per 3.5 square inches of surface area. If the current is lower, you may have to increase the time. Best of luck, Ken.

Sebastian

8/29/2013 04:22:56 am

Hey Ken

first of all, id like to thank you for this, this has been very helpful, now, i have a question, i did all as said, but for some reason de cathode was not producing any bubbles during the anodizing process, and i dont know if the piece was anodized at all, any other metal i tried to see if everything was ok, was oxidized instantly, i dont know what im doing wrong, cathode and anode were aluminum which i grind with sandpaper and cleaned, and after all this, the coloration did work either i used (12v, 3amp) and (6v, 1amp) i can see the difference a slight difference in the piece since it was not submerged entirely. any ideas???

Sebastian

8/29/2013 04:24:11 am

Sorry for my english, its not my mother language

Ken

8/29/2013 08:56:24 am

Hi Sebastian,
This may take more than one mail to answer your questions as I am a bit confused. If there are no bubbles from the electrodes that suggests that there is no current flow or it is very small. If you have a meter it would be worth checking the current draw first of all. You also say that there is a difference in color between the submerged part which suggests that it is working. How large were the aluminum pieces? And, your English is fine! Ken.

Jeremy

9/5/2013 11:49:32 am

Ken,

I wanted to give a quick update on my anodizing. I stopped for awhile, but have picked it back up. I anodized a part today with some excellent results. I will give my process in as much detail as possible and links to pics at the end.

First and foremost, the use of distilled water is a must for the etching solution, anodizing solution and rinsing. I did the boiling with tap water, but for best results I will use distilled for this as well.

My anodizing mixture consisted of 3 cups of distilled water and 15 tablespoons of the pH down. I used a normal household tablespoon. For the lye, I used draino (estimate 1/2 cup) with 3 cups distilled water. The dye misture consisted of 2-1/2 tablespoons of dye to 3 cups distilled water. I mixed all solutions really well until there appeared to be only one type of liquid in the container. Also, each solution was between 73-90ºF. The lye and anodizing solutions were used in my garage and the dye was used inside my house.

I used a scotchbrite wheel in my drill press to begin with. Not too much time here, just enough to get the part cleaned up and smoothed out. I then used fine steel wool to help smooth the part out a little better. Then, a good cleaning with liquid dish soap and tap water. I used a non scratching pad during this step. Once clean and dried off, into the etching solution it went. I etched for about 5-7 minutes. I also cleaned and etched the aluminum that I used for the cathode to ensure good conductivity. After etching, I rinsed with distilled water (I use a spray bottle). Then, into the anodizing solution. Now, here is where I changed things up a bit from my lsat time out. I used a 14V 25A 350W AC to DC power supply. I think this helped a lot. Plenty of power and current for what I am anodizing here. I let the part anodize for 2 to 2-1/4 hours. Once I felt it had been in there long enough, I removed the part, rinsed and placed in the dye. I kept the part in the dye for about an hour or less. The dye started taking within the first minute of the part being in the solution. After dying, I boiled the part in tap water for about 15 minutes. Maybe should have done longer, but I'm impatient lol.

The part turned out great and the color really took and is really dark. I finished it up with a thin coat of a spray acrylic clearcoat. Check out the pics and I hope this helps anyone else looking to do this.

Oh and the part and the piece used for the cathode are both 6061 T6 aluminum.

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130905_163107_zps62fc79ec.jpg?t=1378413172

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130905_181217_zpsb75be4b9.jpg?t=1378425078

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130905_193339_zps81680829.jpg?t=1378425040

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130905_193231_zps2ab2284a.jpg?t=1378425064

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130905_202733_zps99535225.jpg?t=1378427505

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130905_202753_zps304e0602.jpg?t=1378427480

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130905_202820_zps8f3da736.jpg?t=1378427457

Ken

9/8/2013 01:18:36 am

Hey Jeremy,
I agree with the use of distilled water but the cost can be a problem for some. The long etch seems excessive but the part looks great. It would be interesting to know what the actual current draw really is. Good job and thanks, Ken.

Jeremy

9/8/2013 01:43:12 pm

I wish I had a meter to measure the current. The fans on the power supply did eventually turn on but I'm not sure at what set point they do so. As far as etching time, I just watched it until I could see it had a good etching but didn't want to leave it in there too long. The distilled water I use was purchased at Walmart for$.88 per gallon. Pretty cheap for doing small parts like mine because I don't even use the full gallon. These are my best results so far and am extremely pleased. Next project is deanodizing a part then anodizing a different color. Wish me luck. :)

winston Lee

3/2/2015 08:29:52 pm

How do I access the Photo bucket links in the article above

Robert R link

4/29/2015 02:36:34 pm

To access the links, just copy them and paste them into your browser's address window and hit enter....

Adam G

9/7/2013 03:55:40 am

Would it be possible to mix a solution of citric acid for anodizing too? I have some of that (pure) in powder form. I've mixed it up to clean up stainless steel (for home brewing applications) from time to time. Would just need to figure out what concentration to mix up. This is pure citric acid, which could alter the mix rate.

I'm about to try with the sodium bisulfate (tried TSP the first time with poor results). I also picked up a gallon of denatured alcohol to 'degrease' the part with. I'll post up the results once I get something worth talking about... Oh, and I'm trying to anodize 7075 aluminum, without any color added.

Ken

9/8/2013 01:45:28 am

Hey Adam G.,
It is possible to anodize in just about any acid -- if by anodize you mean make the part anodic and build some sort of film on it -- because almost any acid will conduct electricity. But the characteristics of that film will vary tremendously based on all of the anodizing conditions and they would not approximate the film formed in either sulfuric acid or sodium bisulfate. Remember that in anodizing the sulfuric acid attacks and dissolves the anodized film, leaving a honeycomb type structure, and other acids may not dissolve the anodizing that way.
Tartaric acid, phosphoric acid, chromic acid and boric acid are a few of the commercially used acids. But the coating does not look or function anything like a sulfuric anodized surface. Check the link on electrochemistry for more information. Ken.

Adam G

9/8/2013 11:42:48 am

Interesting info.. I think I'll just stick with the sodium bisulfate for now. I do plan on getting another container of it (or two). I did weigh the 2-1/2 tablespoons worth of the stuff to find out the weight. I'd rather go by weight with dry elements rather than volume. Same thing for the NaOH mixture. Turns out I needed to use 7 grams of that per 3/4 cup of water (the NaOH). I have the sodium bisulfate amount downstairs. Came out to needing 1800 grams for 2.5 gallons of water. So just under the 5 pounds I bought initially.

For the water supply, I'm running water from my filtration system (goes down to .2 microns) through a DI filter element. This is costing me virtually nothing, since I had the filters and was given the DI filter (along with refill media). I set up the connections onto the filter with hardware I had on hand. Considering how much water I've run through already, using distilled could get costly.

I'm also using a denatured alcohol bath to remove any residue on the aluminum before I start the processes. After these first pieces, I want to anodize more. I also want to get some different color dyes to use on things. I also plan on using some 6061 plates for the cathode. I'll run them around the inside of the the bucket, linking them together with a wire (or two) so that I don't need to worry there. Since I have some plates on hand already, it shouldn't be much of an issue.

Dan Damaia

6/1/2023 06:36:34 am

I tried citric acid and no luck at all - waste of time - really disappointed after all that prep work - I didn't think I could do this at home.
I tried the second time with the PH down and it turned out pretty good.
its a great feeling to see it pay off when you dip your part into dye and it sticks right away.
I also tried a 2 tone trick where I placed 1/4" high letter stickers to spell my logo and then glass blasted the surface leaving the covered area polished. After blue dye the letter area was a shiny finish and the blasted area was a matt finish the letters looked really cool.

Richard

9/16/2013 02:34:24 pm

Hi, I'm successfully anodizing with sodium bisulfate at 30%, with excellent results usig the 720 Caswell rule, the only question is, how long it will last the solution?? And how can I check it? My anodize tank is a 5 gallon bucket.

Ken

9/17/2013 08:28:18 am

Hi Richard,
There are three general ways that the solution can fail. The first is by acid depletion over time, the second is by acid increase by evaporation of the water, and the third is by metal contamination caused by either poor quality anode or cathode. My suggestions include the use of universal pH paper (available online), testing specific gravity with a hydrometer, (you can make one with a straw, just Google homemade hydrometer), and using a small piece of scrap aluminum of the same size before each real run of anodizing. Save the test pieces and compare them over time. I prefer the last one as the results will be obvious when there is a degradation in quality. I am glad that the system is working for you and thanks for the question. Ken.

Adam G

9/17/2013 10:27:32 am

Ken,
What if you have both refractometers and a hydrometer (for homebrewing applications)?? Will those do any good in testing? I do have one refractometer that I really don't care about (a cheap one). What should I be looking for, in the solution?

I plan on getting some more sodium bisulfate this week, so that I can make up more solution as needed. Just would help to have a better idea of when to change it without wasting any on anodizing items that are 'scrap'.

Also, is there any way to get a harder layer on the aluminum with this method? Something closer to type III would be great. Right now, my main concern (for type III) is with 7075 aluminum. I do have a piece of 6061 that I'll be anodizing later (will want the harder layer on that too).
/Adam

Ken

9/18/2013 08:33:42 am

Hey Adam G,
Refer to the previous reply to Richard for some quality parameters. The refractrometer and specific gravity for home brew will probably be to low a scale for anodizing solution as the SG is about 1.2. It does occur to me that the easiest and cheapest SG test can be found at most automotive stores in the form of a battery acid tester. Hard anodizing is usually a thicker film, done cold, and requires tighter control and is not sealed or dyed. Here is a link to the process: http://www.arrowcryogenics.com/hard-coat-aluminum-anodizing.htm. Thanks for the questions, Ken.

Jeremy

9/19/2013 11:51:26 am

Ken, I have some great news! I was able to successfully anodize a part in black! The part turned out great! Below are pics. I also tried something different today. I used aluminum foil (Walmart brand) as the cathode and was still able to anodize the part well enough to take the black dye. Couldn't believe it. I also mixed up a fresh acid solution. 15 household tablespoons of ph down and 3 cups distilled water. I used the same power supply. This time around I did not etch the part and it still turned out great. This method is solid once you work out little kinks. Thanks so much, Ken!

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130919_213508_zps58700d4d.jpg?t=1379641458

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130919_213525_zpsd92aee35.jpg?t=1379641444

Ken

9/20/2013 08:37:35 am

Well done Jeremy! The part looks good and as mentioned before black is the most difficult. I am surprised that the aluminum foil worked well as it is thin and degrades quickly. I am currently using aluminum flashing that I form into almost a full circle inside of a round container so the the cathode goes almost all the way around the inside of the container. Seems to provide very uniform anodizing. Nice job and photos, thanks, Ken.

Jeremy

9/23/2013 05:26:52 am

Thanks, Ken! I was so happy when the black turned out better than expected. I have a new anodizing "tank" now. I am using 3 gallons of distilled water and 15 cups of ph down. I still need to refine this setup as far as connecting the anode lead and I am still using aluminum foil as well. I went to a larger size tank to do multiple parts at one time, so they will hopefully all turn out the same for the end result. I think I'll try to find some ph paper, so I can keep an eye on the condition of the anodizing solution. With over 3 gallons worth, it would be rather expensive to keep replacing it. I should be able to add to it if I lose some due to evaporation and what not. Here is a pic. Let me know what you think.

http://i1032.photobucket.com/albums/a409/ponie1992/RC%20Stuff/20130923_150947_zps32a8943e.jpg?t=1379963450

Ken

9/23/2013 08:16:39 am

Looks good Jeremy but I would be concerned about evaporation with that much surface area. Unless of course, you have a cover. You could also make a mark for the current liquid level but I would pick up a battery tester for car batteries and use specific gravity. Decreasing water = higher pH and depletion of acid = lower pH. Just a thought. Great photo! Ken.

Jeremy

9/23/2013 12:38:35 pm

Ken,
I do have a cover. We'll see how it goes. My main concern is evaporation, but hopefully I won't lose much. I'll get a battery tester as you suggested. I have marked the container, so any decrease in the solution should be easily identified.

Richard Clark

9/27/2013 02:49:49 pm

Hi Ken,

I bought some ph paper and the result was between 1-2, also I get the hydrometer from Autozone, and the mark says between 1225-1250, as I told you before, the solution is working with excellent results, I prefer using the sodium bisulfate than the sulfuric acid, in my opinion is safer, but SB is more expensive, anyways I'm very happy.

Here are some of my results with clothes dye.

http://i63.photobucket.com/albums/h146/best_panther/61211D1A-888A-49F0-9C8E-15B170F60229-3205-00000317B5FFF822_zpsc67a61fd.jpg

http://i63.photobucket.com/albums/h146/best_panther/4121D3C4-6425-451B-85D6-B5C2CDE48C1E-5257-000005498A17C10E_zps1f22d9e6.jpg

http://i63.photobucket.com/albums/h146/best_panther/D78CDA7F-D545-466D-91A5-CBAC4222126D-1661-0000019E329E89BA_zpsed476136.jpg

http://i63.photobucket.com/albums/h146/best_panther/3B150B19-554A-431F-ABD8-7F9278FB98E6-5696-00000561FC0D242D_zpsa2d9ec04.jpg

http://i63.photobucket.com/albums/h146/best_panther/E6405607-6609-4373-AEF3-1DA672BBE1D2-2391-000003693D909F23_zps31834ba6.jpg

Thanks, and greetings from Guadalajara, Mexico!!!

P.S. Sorry for my bad English!!

Jeremy

9/28/2013 01:28:33 am

Richard,

Please share how you are achieving the shiny finish. I want the same results without having to use an acrylic clearcoat. Your anodizing looks great!

Richard

9/28/2013 01:40:57 am

Hi Jeremy

I'm not using a clear coat or nickel acetate just boil distilled water for 30 mins to seal, and to get the shiny look, just polish the aluminum before all the process (if you polish the aluminum, don't use lye).

Jeremy

9/28/2013 02:41:17 pm

What type of polish and polishing process are you using? What are you using to clean the part before anodizing? Thanks.

Richard

9/28/2013 03:00:49 pm

I'm using a buffing machine with white tripoli compound ( you can also use white car polish).
To clean the parts, I use dish detergent, degreaser, and 30 minute in boiling water with (again) degreaser and dish detergent, then 5 second bath on muriatic acid.

Always rinse with distilled water before and after each bath.

Jeremy

10/2/2013 03:27:06 pm

Wow, that's quite the process. I tried out a little polishing before anodizing and got great results. Thanks for the tips. I did it a little different. I used mothers polish and a polishing wheel on my dremel. I didn't polish to a mirror finish, just enough to get a decent shine. After polishing, I cleaned the parts in dish detergent and scrubbed with a tooth brush. Rinsed and then let soak in rubbing alcohol. Pulled straight out of the alcohol, sprayed down with distilled water and into the anodizing tank. My parts look so much better with a little shine vs etching before anodizing.

claudio

10/4/2013 03:29:09 pm

HI, can you Help me I never tried nothing like this, but I'm working in a aluminum tool box and it would be great to anodizing it. The box is 25*30*15 and it has the cover that is aprox. 25*30*5 and I want to see if you could help me with the voltage and mixes I need, thanks

Ken

10/5/2013 09:28:20 am

Hey Claudio,
I am assuming that you are talking in centimeters but that is still a large area to anodize. My suggestion is that you experiment with some small pieces to learn more about the process. There is a lot of information in the post and the comments and if you have no experience with anodizing, taking it slow might be the best approach. Thanks for the comment. Ken.

claudio

10/5/2013 11:13:55 am

Yes it's centimeters I want to know is how much power will I need to do it, I know I will need some experimentation but will the setup I need for the larger part have the same results as the smaller parts or I need to change the amps ? The thing is that I don't know the peer supply that I will need for such a large part

Ken

10/6/2013 01:20:23 am

Claudio,
The current required for anodizing in general is very much a variable, but a guideline is 2.8 to 10 amps for one square foot of aluminum. This process is very open to experiment and optimization. Convert the area in centimeters to square feet and use appropriate amperage at between 6 and 12 volts DC. Use a 20 t0 30% sodium bisulfate solution. Ken.

Paul Schlichtholz

10/29/2013 10:12:40 am

Dear Ken,
I just finished reading your article on anodizing and dyeing aluminum and was compelled to write and tell you how much I enjoyed it.
I was searching the web to learn about how to anodize as it is new to me and came across your instructions. I am now very confident that I will be able to anodize and dye what ever parts that I need to.
I just wanted to thank you, and also the patience you have when answering all of the questions that your readers have is very nice.

John Wizman

11/21/2013 09:11:11 am

If I was to anodize 50 sq inches of aluminum at a time, you think I should concern myself with cooling the solution?

Ken

11/22/2013 01:06:29 am

Hey John,
Research has indicated that thicker films are formed at low temperatures, and take dye better. My own sense is that it would be best to keep the temperature below 100 Fahrenheit. But, I would not plan on a cooling process but rather start with room temperature and it will rise naturally as the anodizing proceeds. Allow cooling between runs as anodizing does raise the temperature. Hope that this helps. Ken.

John Wizman

11/26/2013 09:25:54 am

First I want to start with a glass bead blasted finish. Have any suggestions in the event I have to desmut my parts? I have muriatic acid and aluminum sulfate in my arsenal. If necessary I would desmut my parts then run in the tumbler with soap water . dunk in acetone and then dunk in denatured alcohol. Sound like a good pre anodizing game plan?

If I ran the anodizing tank in the machine shop, will that corrode my machinery? Or should I do it completely in the back yard?

Ken

11/27/2013 12:45:55 am

Hi John,
I would suspect that desmuting would only be necessary if the air pressure is too high and caused glass breakage and imbedment of particles. With 6061 aluminum I think that 80 PSI might be adequate. As far as pre--treatment goes, the simplest is best so that it is repeatable. The soap and water, acetone regimen sounds appropriate. As far as machine shop practice, the only material leaving the tank will be water as evaporation occurs. So, rust would be a concern only if there is a lot of evaporation which seems unlikely. Thanks for the questions, Ken.

JOhn

11/27/2013 03:07:23 am

These particular parts I am making right now never had a tag or marking as to what grade they are. Could even be 2024.

Armand

12/13/2013 12:42:01 pm

Hi Ken, I just want you to know that your blog about anodizing aluminum has been of immense use in teaching me how to do this at home in my apartment. I know that I haven't read ALL of the comments placed here but enough to get me by some if the tough spots. I did start by using the RIT black dye and when it turned out to look a brownish/bronze color I was very disappointed and tried several times altering this and that to see if I could get it black but had very little success. After doing a lot of searching on the subject I found out that RIT dye will never give a true black color as the end result. However, I did see on the web someplace that a guy used Dylon black dye (has to be the multiple-purpose dye) to do his gun parts and he posted photos of them which showed as true black. So I went out today and bought some Dylon #08 Black dye and did a sample piece and sure enough it came out as black as the ace of spades. I was quite happy with the end result. Now I just have to find someplace local to get some 1200 or 1500 grit sandpaper because the scratches seem to show better through this dye..

Anyways, thanks for doing the work and sharing it with the world. :)

Ken

12/14/2013 12:37:18 am

Hey Armand,
Thanks for the comment and great information. I have recommended the Caswell before dye to get true black but this seems like a good alternative, as the Caswell is pretty pricey. Thanks for the effort and result. Ken.

Steve Ryan

12/14/2013 03:16:02 am

Ken , first off Great article ive been woried about trying this but i feel much more confident now. I will be anodizing 7075 T6 forged aluminum. will this change the process much as far as times/concentrations/volts/amperage ?
also I am trying to achieve a dull or flat finish. what is your recomendation for surface prep i.e. raw/brushed/bead blasted etc
Third question is directed to Armand; is the Dylon dye the clothing dye?

Adam G

12/14/2013 03:28:59 am

Steve, I've anodized 7075 T6 forged aluminum 'parts' with this method. If you do a lye bath/soak you can get a decent flat finish. I did a couple of pieces that the owners glass bead blasted with good results (got the texture right). Be sure you clean the items before you start the process though.

If you're thinking about doing the same forged items I've done, then you'll need a large enough cathode. I'm using 8 3" wide, 1/2" thick, plates that are fully immersed in the sodium bisulfate solution during anodizing (longer than needed, so parts of them stick out). I'm using a battery charger from the early 80's for my setup. Simply, it works really well.

I will say that you do need to double up the dye concentration for water volume listed. This even applies to dye from Caswell. Let it soak until you have the color level you want.

I believe it's been mentioned before, but do some testing before you do a piece you care about. That being said, you can simply give the piece a soak in the sodium hydroxide to strip the anodizing from it and start over again.

Steve Ryan

12/14/2013 04:16:29 am

cool Adam , thanks for the input

George F. link

5/15/2015 04:37:12 am

Hi Adam,

A couple of questions for you. After the lye bath did you need to desmut the parts prior to anodizing? Also what current setting are you running the battery charger at and for how long? I just tried anodizing a forged 7075 T6 part and it came out with a varying layer of anodizing, some of the surface didn't have any (no resistance when checked with an ohm meter) and some surface was anodized (though it still didn't take the dye very well). I set the part in a lye bath for 5 minutes and rinsed with distilled water. I'm using a large piece of 6061 for my cathode, aluminum wire to connect and I had my battery charge set at 10A for 60 minutes. I am concerned that the lack of a desmut operation caused the uneven layer of anodizing. Any thoughts and suggestions would be greatly appreciated. Thanks!

John

12/18/2013 08:56:41 am

I was wondering if my idea for a anodizing bath hanging system will work. I have 15 awg copper wire running through the tub about 3" above the bottom and I plan on lining the bottom with lead for the cathode.

Here is a pic
[IMG]http://i40.tinypic.com/2yuactc.jpg[/IMG]

you can see how I drilled a hole for the wire which is copper and where teh titanium hangers are holding the parts. The parts are not held tightly by the titanium just a contact is made, on teh other hand nothing will fall out. But I must ask, will that suffice in regards to conductivity?

Will any of the solutions that I am going to use in this process need special containers for storage? I plan on using lye, desmutting from caswells and the the PH down stuff.

JOhn

12/18/2013 07:10:12 pm

CORRECTION: When I siad 3' above the bottom, make that more like 1" above the top of the solution. I'm talking about 4.5" total height of the solution.

Ken

12/19/2013 12:33:58 am

Hello John,
I am not sure why you are using titanium, because as a transition metal, it has poor electrical and thermal conductivity. Particularly, if it is small gauge, you may be adding current limiting. I would think that aluminum wire would be better and easy to find. But, in either case, I would wrap two or three turns around the copper wire and clamp the wrap with a clothespin to guarantee good contact. As far as storage containers, any good plastic that can be sealed against evaporation would be fine.Thanks for the questions and good luck! Ken.

Adam G

12/22/2013 01:51:22 am

I reanodized a lower last night. I had done it without any dye, previously, and wanted to add color to it (black)... Cleaned the item, soaked in denatured alc., then a 7-8 minute soak in NaOH to remove the previous anodizing. Gave it a full hour in the anodizing tank, followed by another hour in the dye bath. Then a 20 minute boil in the sealing solution.

Results:
https://dl.dropboxusercontent.com/u/33179624/re-anodized_300_blackout_pistol_lower_1.jpg

I won't tease people with what the completed assembly looks like. Especially for those that live in nanny states that won't allow you to have one. lol

Adam G

12/22/2013 01:51:29 am

Rod

12/22/2013 08:10:21 pm

How well does the Sodium Bisulfate process works for a CLEAR surface finish. Are there any special requirements that would be different than if using the Sulfuric Acid process.

I'm looking for a Satin Semi-Gloss type finsh almost like a brushed staniless steel.

Adam G

12/22/2013 09:39:24 pm

Works well without dye too. I did my lower that way the first time. I would just suggest getting the surface of the aluminum how you want it to look before you anodize it. Also, depending on the alloy, you might get a color change anyway. Even without adding dye.

Ken

12/23/2013 12:44:25 am

Rod,
For type II anodizing, (thin coating), both processes work in the same way. Adam's comment below is true that surface preparation before hand will determine the final appearance. Dull finish before=satin finish after. But, you will still need to boil to seal pores after anodizing to reduce the amber cast color and change the index of refraction. Ken.

John Wizman

12/24/2013 07:41:19 am

OK I wrapped the titanium to the hanging wire and all. I am getting 1 ohm resistance between the hanger wires and the lead plate. I am getting 0 Ohms throughout the hanger and the hung parts. Maybe I should add more PH down till my resistance throughout the solution is 0 Ohms? Or is that not my problem?

Ken

12/25/2013 01:09:54 am

John,
A 1 ohm differential is really insignificant and is within the margin of error for most meters, even low ohms. You should be fine. I would trust the pH more than resistance. It sounds like you have good contact to the parts. Go for it! Ken.

JOhn Wizman

12/25/2013 01:43:50 am

Problem is that my power supply is showing .4 amps at 23 volts after about and hour. I start out at .8 amps. 720 rule said I should I only need 3.5 amps at 15 volts for 1 hr. I am suspecting my AlOx thickness is very thin and besides, I am not getting that many bubbles while anodizing. It just doesn't seem right.

JOhn W.

12/25/2013 01:45:51 am

I am using a 3020 EQ power supply. I didn't pay $250 for a PS so I can anodize at .8 amps 23 volts

Joel

12/28/2013 05:34:46 pm

Hi Ken,
I am trying to figure out where I am going wrong. I completely sand down my Aluminum parts, take a wire brush to them, wash them with dish detergent, and do a final rinse with distilled water.
I place one part at a time of about 1.5” x 1” x 0.25” in the acid bath with 15V, 1.5A. Getting loads of the good fun bubbles from the cathode for about an hour, then it stops. I figured that meant it was done, so I take the part and put it in distilled water then into a strong concentrate solution of tan Rit dye (3dye:1H2O). To begin looking like the desired shade, it takes about two hours sitting in the dye. I put the part in boiling distilled water and just about all the dye gets boiled out, leaving just a small tint of tan that can barely be noticed.
I have tried different types of aluminum and get the same results. Any thoughts? Thanks! -Joel

John W.

12/28/2013 09:09:39 pm

Right after rinsing it out of the anodizing bath, check with an ohmmeter for conductivity. Anodized layer does not conduct. I kinda suspect that your power supply is not sufficient. In my meager experience, it seems like the parts that come out of the anodizing rack slightly dark dull gray take color the best.

Jeremy Stillson

12/28/2013 09:10:45 pm

Joel,
Sounds Like you're losing the electrical connection. In my experience with Ken's method, it takes about 2 hours to get a good anodized layer. With a good layer on the part, the dye should start to look dark around 10-20 minutes. How are you securing the electrical connection?

Ken

12/29/2013 12:38:22 am

Joel,
Two tings jump out to me at the same time. The first is that the dye may be fugitive meaning that it decomposes under heat, Have you tried another color? The second is the cell size. Check the link to cell development in the write up for the encyclopedia of electrochemistry. Ken.

Joel

12/31/2013 11:43:36 am

The cathode is connected with an alligator clip. The anode is connected with aluminum wire wrapped around the part multiple times.

Joel

12/31/2013 11:59:27 am

Ken,
Thanks for your help! If I understand right, having lower amps in the power supply would just require longer bath time right?
Also, because the anodized layer is not conductive, if you were to stack two separate heatsinks together that were anodized, would it be smart to take off the anodized layer just between the two heatsinks?
Thanks!

Jeremy

1/2/2014 01:47:44 am

Joel,
I think you are definitely losing connection. No bubbles indicates this. As far as stacking the heat sinks, the anodized layer will resist conductivity, but still transfer heat. If in doubt, then you can always remove the anodized layer between them.

Adam G

12/30/2013 09:57:41 am

Just a FYI for those using this method.

I wanted to push more current into the anodizing process (at 12v). So a friend (electrical engineer) helped me wire up a computer power supply to feed the process. The PSU produces up to 16a on the 12v rails (plenty of power). We were able to get it to power on with nothing connected to the PSU. I got it home and tried it tonight on a test piece of 7075 aluminum. No joy (at all). When I plug the PSU in (no switch on it) and it's connected to the cathode/anode, nothing happens. I let it rest a few minutes, disconnected, and it turns on (fan on the PSU spins).

So, since I really want to use something that I can actually see what voltage and current I'm pushing/using, I purchased a lab power supply off ebray tonight. 0-30v and 0-10a on the unit. Should be plenty of power for anything I want to anodize (with my current tank setup). Even if I go with a larger tank, it should provide enough power to do the job. I hope to see it before the weekend, so I can test with the NFG/bad item.

While I probably could continue to use the old battery charger for this, I'd rather use something that's more made to do the job. I don't want to kill the battery charger by using it as it was never intended. I also don't want to put a 12v battery into the setup. Especially since I'm doing this in the kitchen of the house I'm renting.

Eric

1/1/2014 11:15:47 pm

Hey ken, I have been looking into everything I can about anodizing aluminum and the different benefits and shortfalls of each acid type. my question is this; with the sodium bisulfate do you think that a good corrosion barrier is being created or do you think it is more like a simple aesthetic layer and not very corrosion resistant?

Adam G

1/1/2014 11:26:06 pm

Eric,
It's easy to test with a multi-meter. Anodized aluminum will be non-conductive (this is what prevents corrosion and such).

Also, it's been pointed out (read it someplace, don't recall exactly where) that you can anodize without coloring, but you can't color aluminum without anodizing it. If you use a power supply that's good for your piece size, mix the sodium bisulfate to proper strength, you'll get a great protecting layer.

I would also look up the constant current method of anodizing. Seems like you can get a great result with much less time spent that way.

Jeremy

1/2/2014 01:50:05 am

Eric,
I believe this method creates a good corrosion barrier. I say this due to the fact that I can get parts to to accept really nice dark, rich color. I would think if the layer wasn't good, I would not get the great results that I have.

Eric

1/1/2014 11:39:14 pm

I forgot to say;
as far as I have found, sulfuric acid creates the best corrosion resistant barrier. do you think that sodium bisulfate creates a comparible effect?
ps. great stuff man, this is really helping a lot.

Eric

1/1/2014 11:46:29 pm

Thanks Adam.you reminded me of the obvious. lol
however, I have read that acids such as phosphoric acid will anodize aluminum but the oxide layer is very weak and very poor at resisting corrosion

Adam G

1/1/2014 11:51:42 pm

So, use both methods and then compare. For my use, it's doing a solid job. I'm not putting the items into a hostile environment or anything like that.

IMO, the fact that you don't need the protective gear, or ventilation system with sodium bisulfate (compared with the other acids) makes it well worth it. Plus, not getting the hydrogen gas cast-off from using sulfuric acid is not a minor item. I don't want to blow up the house after all. I also don't have a spot outside (or a garage) to do this in. I'm doing it all in the kitchen in fact. Where I have the water filtration system setup (to produce DI water).

Eric

1/2/2014 12:05:23 am

Right, i hear you.
my interest in anodizing is for use on a car (substantial exposure to the elements) hence the importance of the most corrosion resistant effect.

Adam G

1/14/2014 09:14:40 am

If anyone cares, or has issues with using volume measure for dry items, I've figured out the amount of chemical per gallon...

Sodium Hydroxide (NaOH) at 2% solution is:
77.32 grams to one gallon (128 fl. oz.) of water.

Sodium Bisulfate (NaHSO40 to water at 20% solution is:
946 grams to one gallon of water.

IME, it's always best to keep dry items in weight and then liquid either volume or by weight (when weight is constant). Since different grain/particle sizes seriously impact dry measure, weight is ALWAYS more accurate. While it might not seem important to many, when dealing with things like this, I feel getting the correct solution is important.

Ken

1/15/2014 12:50:04 am

Adam G,
You are absolutely correct and perhaps I should have included the weights. But, thanks to you for the effort and comment. Ken.

Adam G.

1/15/2014 02:10:29 am

I did think it odd that you didn't have it listed as such originally. Especially since you provided grams to ml. With conversion software (on my phone of all places) and a calculator it wasn't too much work to get this done. With what I'm anodizing, I need gallons of solution mixed up.

I did want to ask if it's possible to use the sealing solution (powder sold by Caswell) once fully mixed, at room temp. The stuff has a bit of an odor to it, that seems to migrate to the second floor of my place, and linger for a bit. IF I could use that at room temp (even if it's for a longer time frame) or at lower temps, that would be great.

I did re-anodize my 'test' piece yesterday. Tried using the new power supply, but the fuse at the power in popped on me. I have more of those coming today, so I can give it another try with something else. I ended up using the old battery charger, not really going by time, more by look and sound. You can hear the difference in the charger when it's not pushing power like it was before. Which we used to use as another measure that the battery was fully charged. Plus, the reaction inside the tank had gone to pretty much nothing. I didn't use the sealing solution this time, after giving the part a nice soak in the black dye tank. After letting it dry overnight, it looks pretty damned good. My only 'concern' is that the dye might run if it gets wet again. I might try hitting it with some tap water to see what happens with it.

Here's how it came out:
https://dl.dropboxusercontent.com/u/33179624/latest_anodize_test.jpg

Ken

1/15/2014 07:37:42 am

Adam G,
Fantastic job!The sealer that you are using, if green, is probably nickle acetate which liberates acetic acid on heating. I really see no reason not to use boiling deionized or distilled water as the result is as good as the nickle acetate. However, it may be a proprietary sealer and I have no good information as to operating temperatures. There are some "cold sealers" available that seal by literally filling in the pores mechanically, like a Teflon polymer solution. But this seems like a poor choice for you. So, it is either venting the current sealer or water. I vote for water! Do let me know what you discover as your comments add to the discussion in a really good way. Ken.

aborza

2/1/2014 02:20:10 am

Hi, Great DIY contribution. Kudos.

If I understand it properly, this is a "soft" anodizing process vs. a "hard" anodizing process. Soft being thinner and less protective in a harsh environment. I wonder if before sealing there could be a dip used in place of dye that could then be sealed inside the crystalline structure to provide for harsh weather protection. I am thinking of some sort of common water repellant, anti corrosive or very thin oil.

If this is possible I could then rehab some Al parts that have corroded on my bicycle here in the Gulf Coast of Florida salty air.

Thanks.

Ken

2/1/2014 08:32:53 am

hi Aborza,
You are absolutely right that this is type II (soft) as opposed to type III, (hard) anodizing. Hard anodizing requires higher voltage/amperage, and a chiller to keep the solution at around 32 F. Hard anodizing results in a darker finish and can only be dyed with dark color. But, I would think that for your conditions this process would protect as well unless the conditions are really brutal. I cannot think of any material that can be applied before sealing to increase resistance. However, a coating after dyeing and sealing could increase the appearance and resistance. I am thinking about something like a silicone, (Armor All) or other coating. Hope that this helps and thanks for the comment and question. Ken.

Adam G

2/1/2014 08:51:33 am

How much more current/voltage?? I have someone building me a power supply that should be able to produce up to 28v and up to 30a of power. For type III, and I looking at double the current of type II? Also, what's the +/- on the 32F parameter? I'm sure I could clear out the fridge in order to get the solution closer to 32F (overnight). Or rig a freezer to maintain the temperature (would have to do that later. Maybe even get to the point of using a peristaltic pump to run the 'warm' electrolyte through a plate chiller (or some kind of chiller configuration) to drop it closer to 32F... Right now, I could get it close with using the fridge to pre-chill the solution, then use ice in a cold water bath to keep it close to the target.

Oh, and I hope to use the constant current model with the new power supply...

Ken link

2/2/2014 12:15:19 am

Hey Adam,
I have tried hard anodizing and had very poor results because of the temperature control needed. It is fairly difficult process condition. Rather than provide my take, I have added a link to the Caswell forum that has four entries that answer your question. The link may have to be copied and pasted as making it active is not certain. Thanks, Ken.
http://forum.caswellplating.com/anodizing-questions/1751-hard-anodizing-vs-normal-%3B-differenc.html

AG #2

2/6/2014 02:05:11 am

Funny how a commenter has same first name and last initial as me. So to keep things simple I will be AG #2.

I was recently given about 3,000 + arcade tokens from a friend of mine who owns an arcade. He wanted me to make something interesting out of them and the project in mind would need to change the colors of the coins. I see that the process seems simple enough that most anyone with a lack of electrochemical knowledge would be able to pull it off.

How would I be able to use this process on coins? I see that most anodizing methods have the alligator clips not submerged within the solution.

Will this be an issue and if so how would I be able to properly anodize the coins with I guess an 'even chemical reaction (even coat?)' before leading to the Dye solution?

Will I have to take into account how big the token is and the current used? I bought a 6 volt battery for this. I don't know how much it will effect the process seeing that the tokens are small. Each coin is 7/8" in diameter and about a nickel's width.

Thanks for the tutorial I was very happy to stumble across this alternative compared to the highly corrosive process.

Ken

2/7/2014 01:47:25 am

AG #2,
This is an interesting question as making anode contact is required for the process to work, but the method of holding objects can be a challenge. My first thought was that making a holder to grab the coins by the edge would be possible. For example, between two pieces of aluminum channel. But, that seems a bit complicated so I would propose the following: Pick up some aluminum window screen material at the hardware store and make a shallow basket. Allow one edge of the basket to be long enough to reach out of the solution to attach to the battery. Lay the coins, maybe ten or so coins, on the bottom of the basket and suspend over the cathode on the bottom of the solution. Anodize for 10 or 15 minutes and then turn the coins over to do the other side. You may not even have to turn the coins. That is my best idea so far but I will think some more. The current will be dictated by the number of coins so you will have to experiment with that. And yes, the basket will also be anodized. Use gloves with the handling and perhaps others will have more ideas. Thanks for the question, Ken.

AG #2

2/12/2014 10:22:47 am

So I gave it a go today because I had got all the materials and was excited and got poor results. I understand that I need an equal surface area for the cathode and anode, that might have been a place where I went wrong. I tried to get them equal, but it was hard to gauge when I used a piece of aluminum as the cathode and made a wire basket to place coins in. I will just have to expirement more with it. One thing that I did notice was as soon as I connected the battery the chemical reaction immediately took off. I saw an immense amount of hydrogen bubbles coming off the cathode. Within 30 seconds I had that yellow tinge in some areas and others nothing. I decided to let it go for about another 3-5 minutes until I realized the coins were turning red to black. I might have too strong of a battery. Thoughts?

AG #2

2/13/2014 08:11:44 am

So I went ahead and tried again today. I got very similar results even after thoroughly cleaning the coins. One interesting thing i noticed was that the closer the coins were to the cathode the quicker the coin was anodized. I still had very uneven coats but i decided to let them go and examine each one afterwards. I had one that went completely black and was flaking black material into the sodium bisulfate solution. When pulling that one out I rinsed all the black material off and got a pastel red all around the coin. I went ahead and threw what I had into the dye bath for an hour with no real results. I kinda expected that seeing as I still received no yellow tinge. When I was cleaning the coins inside I realized taking off the excess pastel red surface with a scotch brite pad it reveaeled the yellow tinge I believe you're talking about. I'm throwing it in a dye bath now to see if there will be any change to color. Will notify later of my results.

Adam G

2/13/2014 08:21:09 am

AG #2, did you give the 'coins' a long enough soak in NoAH to remove what was on them before?? Or media blast them to remove the previous treatment??

JOhn

2/10/2014 07:43:13 am

Too many cooks ruin the soup. Last time I anodized I got some white spots develop after a few days. I'd wipe it off it would reoccur. I went online in a quest to do something about that. I learned that Dye PH should be around 5.5. That seems to be a big misnomer if using RIT black. Don't mess with the PH. At best just check a fresh batch and try to keep it at that level.

Now, I don't know if this should have any negative effect. Right after anodic bath, I dunk the parts in a Baking soda distilled H20 bath and then a straight distilled H20 bath. Then dye. I do this in order to not introduce PH change.

How do I know that my dye is messed up. Dye won't catch and I checked the parts for anodized layer with my Ohmeter. No conductivity, so I have an anodized layer but dye won't catch.

Adam G

2/10/2014 07:50:45 am

I simply rinse the part(s) off with DI water between steps. I make sure to run the water long enough, and over all of the item, to rinse off anything that's holding on from the previous step. Has worked really well for me, so far.

I would try an item, or two, without the baking soda bath/rinse step, just rinse the item off really well and then put into the dye bath.

Last item I did, I just let it soak in the dye for as long as it needed. I don't need to get these things done fast, at that point since it's not using any resources that cost money (power).

I would also suggest retaining the sodium hydroxide solution even after it's gotten too dirty to be used. If you have a drain that's slow, pour it down that.

Ken

2/11/2014 03:52:33 am

Hello John,
Two things to consider: RIT dye is typically used to color natural fabrics and requires a mordant to form a complex to bond to the fabric. Rit dye is variable in composition. Having said that, I suspect that the white spots are being cause by a contaminant that has not been removed and either closing the pore or interfering with the dye. The pH of the dye should be irrelevant. I generally agree with Adam G that the NaOH pretreatment might help. The other possibility is in the composition of the aluminum. It may have impurities. This entire process is an ongoing learning experience for us all. If you determine the cause of the spots please post to let us know. Thanks, Ken.

JOhn

2/11/2014 04:50:55 am

Well, those parts that I just anodized 2/10 and sealed without dying them had no white spots appear. That means that the problem must have been in the dyeing. I guess that this time by neutralizing the parts out of the anodizing bath and then rinsing them I got rid of that problem.

Ken

2/11/2014 07:38:25 am

JOhn,
Great to hear the solution that you arrived at but I am still perplexed by the neutralization step. But hey, you can't argue with success. Thanks for the reply. Ken.

Ken

2/13/2014 08:29:53 am

AG#2,
Apparently your comments were rearranged and I missed the first but I do have some thoughts about the problems. First, the anodizing seems to be drawing way to much current and causing a soft film and rapid oxidation. Your observation about the distance from the anode to cathode is part of the problem. We can fix that easily but I am wondering about the composition of the coins. Have you tried other pieces of aluminum scrap as a test? Also, you can add resistance to the circuit by adding a small bulb in series with the + lead to reduce the current. Additionally, you can reduce the electrolyte by adding water to lower the percentage of Sodium Bisulfate to slow down the reaction. And finally, as aluminum is anodized, it become more of an insulator and will consume less current. Sounds like you will get there with some good thought and work on your part. Hope that this helps. Do keep us informed to help us all. Thanks, Ken.

JOhn

2/18/2014 06:37:00 am

New observation. when I put the dye powder in the water at the beginning the PH is 10. So I'll do whatever I can to keep it there. ( IE rinsing the parts thoroughly after anodizing). In case I have to lower the PH what should I use? In addition, the 720 rule is sacred. I have a power supply with led displays and knobs or CC and CV. I see that too much power will just cause a lot of bubbles and the part to get eaten up somehow ( the anodizing was wearing down). Keep that current within 10% of the 720 rule. And take 15 seconds at the beginning in order to ramp up to the current necessary. I also see the need to after dyeing the part for a long time to first steam the pores closed for about 3 minutes then to dunk the parts in the boiling bath. You leach out less dye like that.

Ken

2/19/2014 07:59:52 am

JOhn,
Sounds as if you have a really good handle on process control and the tip about steaming the part to fast seal is great. I am still baffled by the pH of the dye however. The filling of the pores is strictly physical and not electrochemical, so pH should be irrelevant. But, having said that, I am always open to rethinking a process. If you had to lower the pH of the dye you might be able to use the sodium bisulfate. But, not knowing the dye composition makes a valued comment difficult. Thanks for the update, Ken.

John

3/14/2014 02:38:27 pm

Hi ken...first let me say "thank you" for this tutorial. I've had great results so far but wanted to ask about reuse of the sodium bisulfate solution as I have a lot of pieces to dye. Have you tried reusing the solution?

Ken

3/15/2014 01:34:24 am

Hi John,
I typically do not reuse beyond a reasonable point. The main factors are maintaining pH, and concentration of the active bisulfate. The solution does change as H2 forms at the cathode and O2 at the anode. Unless cost is an issue, I would replace periodically. You could use a small square test piece and check conductivity and dye acceptance. If the test piece accepts dye and is non-conductive, the solution is fine. Hope that this helps as it is a judgement call. Thanks, Ken.

john

3/15/2014 03:37:53 am

Thanks Jen, yes that is a help.
One last question... I hope it isn't a dumb one. I assume I can use my cathode more than once correct? I cleaned it after my first batch and I don't seem to be getting many bubbles now. That's mostly why I was asking about refuse of the sodium bicarbonate.

Adam G.

3/15/2014 10:09:13 am

IME, lack of bubbles is typically either an issue with the power supply, or connection to the cathode. If your cathode is a single piece, check to make sure the wire going to it is making a SOLID connection. You can also check to make sure the power supply is still working 100%.

What are you using for a power supply and cathode in your configuration?? The ONLY time I had low bubble count (after the initial ramp-up time of a minute or two) was when the power supply wasn't right.

As for when to change the sodium bisulfate, it does depend on usage. As you anodize you'll deplete the active chemical concentration. Unless you depleted it after one use (could be done if you anodized a lot per volume) chances are that's not the issue you're having. I would try adding 3-5% more sodium bisulfate to the tank solution as a test. Or you could just change the entire batch if you've done enough with it already.

Personally, I change it when it gets contaminants in the bath (after the batch that caused it). Or when it takes too long to anodize a batch. I found low priced mix at Lowe's (about $8/5# if I recall) within the last couple of months. I'm mixing up 4 gallons of solution at a time, so finding good priced chemicals was critical.

BTW, what's the sodium bisulfate concentration in what you're using?? You want over 90%. I believe the batch from Lowe's was over 92% (might have been about 94%).

I have a media blasting cabinet now, so I plan to blast my cathode from time to time to help keep it 'fresh'...

Ken

3/15/2014 09:36:25 am

John,
The cathode is reusable with cleaning as you suspected. But, it sounds as if there is an electrical problem. Either there is a poor connection, or the current is too low. In your post you mentioned sodium bicarbonate. I hope that this a typographical error as it is sodium bisulfate. If it is not a connection or current problem try another piece for the cathode. But this seems unlikely. Ken.

john

3/15/2014 03:10:10 pm

Hi Ken, yes that was a typo as you suspected. Its strange because my first true at this was great, but subsequent attempts have had poor results. I'm guessing your correct about the current being subpar . I'm using a car battery charger that has some various settings to control voltage.
Thank you again for this tutorial
Johm

john

3/16/2014 10:32:19 am

Hi Ken, you hit the nail on the head. My power source went bad. I swapped it out and I'm back in business. Lots of tiny tiny bubbles!
Thanks again for all the help

Adam G.

3/16/2014 11:25:37 am

John, what charger were you using for your power source??

john

3/16/2014 12:45:27 pm

Hi Adam, I was using a 12v/6v car battery charger. It has a few voltage/amp settings I could experiment with. To finish the batch I just hooked it straight a car battery which I thought would work fine, but only one of the the pieces (all three identical) took dye. Its strange, but I at least know my power source is the issue (for now anyway)

Adam G.

3/16/2014 12:51:26 pm

If the pieces didn't take dye, then they were not anodized. You can anodize and not dye, but you cannot dye without it being anodized.

I've had decent results with a battery charger from the late 70's/early 80's (without any of the fault protection in it). Newer chargers don't work well, if at all.

My new power supply has displays for the voltage and current being sent through the circuit. I'm finding the resistance is greater with just a single piece, compared with two (haven't done more yet).

John

3/16/2014 02:50:36 pm

Hi Adam,
Yeah I'm pretty sure my charger has some sort of fault protection. Any other suggestions for a power source? I can keep using a car battery I guess but the charger seems ideal to me.
Thanks,
John

Rod

3/16/2014 10:26:41 pm

Try using the Car Battery but having the Charger connected to the battery while you Aandize the parts. This will insure a steady voltage. will be delivered throughout the entire process.

JOhn

3/17/2014 07:00:08 am

I have had an experience where I have anodized the parts and dye did not take. Parts showed no continuity when tested with DMM but would not accept dye. I suspect that I anodized on high amperage and the cell structure was too big and the dye just was not being held or who knows what. Later I used the 720 rule and stayed on the low side of amperage and just waited longer in the bath and results with the dye improved.

JOhn

4/23/2014 10:37:46 am

OK this is my 4th time try to anodize these parts. 1st time half the parts came out good. consecutive times I etched in NaOh to get rid of ALO3 layer then desmutted and finally anodized. Parts come out of bath slightly gray and then I boil in dye and when I first pull out parts they look black then rinse in RO water ( 22PPM I use this for everything that calls for water) and spots appear after sealing in steam they come out mostly yellow with a few black spots.

Anyone spotting any problems????? I am losing my mind.

This last time I am dealing with all new chemicals NaOh, new anodize chem new desmut new everything and same problem.

CAD says my parts are 1.8sq inch each X 7 of em 720 rule said 0.4 amps at about 2 hrs. BTW, my voltage after a while instead of going up, it drops.

JOhn

4/23/2014 10:40:04 am

BTW, now instead of lead for anode I am using aluminum screening weighed down by some. powers supply shows .4 amps at 11VDC

Ken

4/25/2014 09:28:28 am

Hey JOhn,
I have read your posts several times and have only one possibility so far. BTW, I am assuming that since it is drawing 4 amps you are doing ten pieces, (0.4 amps X 10 parts= 4 Amps). I have seen this problem before and it is usually in the composition of the aluminum or deposition by improper cleaning. Since you clean so well, the aluminum may have other metal inclusions. But right now, I have no other thoughts about where the gremlin is. Sorry, Ken.

Adam G.

4/27/2014 11:07:17 am

Maybe using the screening is the cause of the issue here. I use solid aluminum plates in my setup. Plenty of surface area and easy to keep clean. I'll probably be taking my anode apart and media blasting all of the parts that get wet before using them again. I can also give them a dunk in acetone to ensure no contamination is present.

JOhn

4/26/2014 10:57:39 pm

actually 1.8 inch square X7 pcs =12.6 sq inches and I am giving that .4 amps for everything. I am wondering if maybe the amperage is to high and then I get a coarse grain that doesn't soak up dye? I am also desmutting so there should not be any impurities. I am sure my problem is either the anodizing bath or dyeing.

Michael

5/5/2014 07:11:26 pm

Hello all and thank you Ken for your work. Today I was at Lowes picking up some goodies and the ph down that I grabbed happens to be 10% sulfuric acid in fluid form. From what I gather, this wont be a strong enough solution know will it? Shall I return it and find some NaOH instead? Thank you in advance for any help, Michael

Adam G.

5/5/2014 11:48:39 pm

IMO, using sulfuric acid presents too many hazards compared with sodium bisulfate (NaHSO4). Sodium hydroxide (NaOH) is used to degrease/pre-etch the parts.

Find the PH down that contains sodium bisulfate, in powder form.

Ken

5/6/2014 02:24:41 am

Hey Michael,
pH Down is a trade-name and is available as both a powder (crystal) form and as a low percentage liquid for use in fish tanks. You will need the crystal form of at least 90% (sodium bisulfate) which is available at Lowes. The NaOH is for cleaning the aluminum (etching before anodizing) and not part of the anodizing process. Ken.

Michael

5/6/2014 06:23:01 am

Thank you gentleman, I had woken up in the middle of the night and shouldn't have been typing. I mistakenly wrote NaOH and I meant to write NaHSO4. Anyhow the pH reducer I purchased yesterday is brand name "KEMTECH pH Minus" and the principal functioning agent is 10% sulfuric acid H2SO4. I know your intention is introduce and educate us on an alterative to Sulfuric Acid which I and many others greatly appreciate. However now I am curious if this product KEMTECH pH Minus 10% H2SO4 will work as is out of the bottle as an electrolyte. Also the Sodium Hydroxide that I have is brand name Roebic Crystal Drain Opener "100% lye", do you approve of this product or would you suggest something else to etch with? Thanks, Michael

Adam G.

5/6/2014 06:51:58 am

You typically use sulfuric acid at 9.25% concentration for anodizing. You'll also need far more safety gear to work with that. Plus, neutralize it before disposing of it. You won't really be diluting the bottle you bought, which is going to drive your cost per item up.

Also, remember using sulfuric acid produces hydrogen gas, which is explosive. It also produces oxygen gas, which makes the hydrogen produced even more dangerous. You'll need beyond excellent ventilation in that area. Plus getting the fume reducing items will be a very good idea (something you add to the solution, plus balls that float on top).

For the lye, you want 100% (lye IS NaOH). I use Red Devil brand via Amazon, since it's sold by a vendor I've used for some home brewing hardware.

IME, getting the correct PH down is far easier and safer. I do it in my kitchen sink after all (in a plastic vessel of course).

Michael

5/6/2014 09:00:09 am

Adam,
Thank you very much. I'm looking for some opinions, ideas, facts, concerns etc. on the following; I've been using a ceramic type of finish product called Cerakote on steels and 70/75 forged aluminum with great success as long as you're meticulous with the prep work you end up with a fantastic finished product. Part of the suggested prep work for Cerakote is to blast the item with aluminum oxide 120 grit or garnet sand and at the end of the process you bake cure the Cerakote at 250*F for 2 hours or you can speed up the process by cranking it up to 300*F for 45 mins. So when working on the 70/75 T6 forged aluminum in an effort to harden the surface I would like to try to etch and anodize, skip dying and go straight to Cerakote. Do you think I will get good adhesion and will it change the oxide structure if I bake it?

Michael

5/6/2014 09:08:55 am

sorry, it said error so I kept clicking submit like a child...

JOhn W.

5/6/2014 09:38:09 am

Ceracoat over anodized layer In my opinion is called keeping it simple and durable.

The oxide layer is very durable and many times my dye didn't take, but since the parts had no more conductivity out of the anodizing tank I imagine I got anodizing but the dye didn't take. But still prep will be a big issue, far more so than what it takes for just painting.

Adam G.

5/6/2014 09:48:51 am

Rule of thumb is you can anodize and not dye but you cannot dye without the item being anodized. If they dye didn't take (at all) then you didn't actually anodize.

For what Michael is doing, type III hard anodizing is the norm. At home, the best WE can get (unless you use different solutions, power supplies, cooling, etc.) is type II.

Cerakote is an oven cure (in this case) extremely durable treatment. It gets applied at .0005" to .001" thickness. There is an air cure that's better for high temperatures (over 1000F) but that also takes at least a week to cure (can take several weeks). They offer clear coating too, which is air cure.

IMO, you're wasting time by anodizing and then applying Cerakote over it. You'd be better off getting your Cerakote process dialed in to get consistent results.

BTW, our initial test runs were done at the 'fast' cure temperatures... So 300F for one hour.

My cure oven (inside it's 24" wide, 12" deep and 17" tall):
https://dl.dropboxusercontent.com/u/33179624/cure_oven_working1.jpg

Rack I made to hang items:
https://dl.dropboxusercontent.com/u/33179624/cure_oven_rack.jpg

Rack in the oven:
https://dl.dropboxusercontent.com/u/33179624/cure_oven_rack_inside.jpg

I'm waiting for a coalescing filter for my compressor to arrive before the next test run is made. Just looking to trap moisture before the air dryer close to the blast cabinet/spray gun...

Bob

6/21/2014 06:49:47 am

You may have tried to use a non-anodizable alloy of aluminum like 4000. I didn't know there was such a thing until I couldn't get dye to take, no matter what I did. Perhaps it was anodizing, but not forming the correct nanostructure to take the dye.

Ed Perry

6/15/2014 09:08:04 am

Anodize in solution @ 20V 10 min dry part use sharpie pens to color (Only use Hi Temp Pro Pens for black) coat 2 or 3 times to get color even. Seal in sodium acetate 20g/L 20 min @ 80 deg. C. Rinse in cold water, Rinse again in Acetone to remove any dye not sealed in. You can use as many colors as you want at one time, do a painting if you like. After seal step they cannot be removed.

Bob

6/21/2014 06:45:02 am

For those that stumble upon this, like me, who are trying to anodize hammond enclosures - stop now. The three I've tried are of some 4000 series aluminum, and are unanodizable. You have not failed, there's nothing you are missing after days of experimentation, attempting to get anything close to the pretty pictures you see. It's just the wrong alloy, too much Si.

Nancy

7/11/2014 01:48:15 am

Hi Ken,

Thank you for your helpful information. I was able to get pretty good results! I'm delighted!! Thank you! I have some questions and a conundrum:

Here's my setup:
1. Cleaned, degreased, rubbed with alcohol. Handled without touching. Checked continuity.
2. Immersed in lye solution 3 minutes. [3C distilled water + 1/2C lye]
3. Rinse with distilled water.
4. Immerse in anodize solution 60 minutes. [3C distilled water + 15TBL Sodium Bisulfate, 95%]
a. Tried both 6V battery & wall wart [6V, 1000mA]. Voltage varied from 6 to 4.
5. Rinsed with cold distilled water.
6. Dye, variable times from 7 minutes up to overnight. [1TBL Rite liquid dye + 1C distilled water]
7. Room dry.
8. Baked at 200 degrees for 20 minutes. Baked instead of boiling for convenience.

QUESTIONS:
1. I've never seen a "yellow tinge", only a lot of very small bubbles. Any thoughts why no color change? Is that a problem?
2. The wall wart "melted" after about 4 hours use. The adapter became very hot and changing shape. Anodes & cathodes were all grade 6201 aluminum, 3/4" x 5" x 1/8". 2 cathodes (-) facing each other on the sides of the container, 1 "piggy-backed" with alligator clip. The anode (+) lays across the top of the container with aluminum piece to be anodized clipped with a wooden clothes pin. Checked voltage on each test. A LOT of bubble activity. I'm guessing the overheating on the adapter was caused by the 1000mAs?
3. How do I check the amps on the anodized piece?

CONUNDRUM:
1. Below is a link of an image with 4 colors. The red & orange are great. However, the Denim Blue (similar to your test) resulted in a beautiful bright purple and Dark Forest Green, a black-purple. I'll try Caswell, but I'm thinking my system is flawed, producing incorrect colors in the blue & green. Any suggestions?

http://www.mycatsheaven.com/kw/kw_4_1200.jpg

Ken

7/11/2014 08:56:35 am

Hi Nancy,
The yellow tinge is simply an indicator and depending on the aluminum alloy, can be difficult to see due to the index of refraction. The dyeing is the test! If it takes the dye, it is anodized. I would also consider the amount of sodium hydroxide that you are using. Your concentration is well beyond the needed amount of 2 to 4%. It may be over-etching.
A wall wart is not a desirable source of voltage/current for anodizing. They are usually only a transformer and a simple bridge rectifier and usually no filter capacitor. And, their ratings are somewhat questionable. But you are probably right that you had an under-current condition. A better choice would be a real DC power supply, a rechargeable 6 volt battery, or a car battery charger. The best way to test amperage (current draw) is with an inexpensive digital multi meter. They are available at Radio Shack, home stores, and hardware stores. The leads go inline and set to read DC amps.
The color achieved is dependent on pore size, the alloy used, and the dye itself. As noted elsewhere on these comments, the RIT dye is variable and difficult to quantify. You could try heating the dye to get better solubility, or as you suggested, try a real dye from Caswell. The other thought that I had is that of sealing with the baking method. I suspect that the baking may not really seal as well as boiling water. Have you done an A/B comparison?
Thanks for the questions and comments and please stay in touch with your progress. Ken.

Nancy

7/26/2014 12:45:13 am

Ken, thank you for your follow-up & helpful suggestions.

I bought a DC variable power supply which hopefully is more consistent and displays amps. I think I'm dyeing but not really anodizing since whenever I boil to seal, the color fades or disappears. I've tried steaming prior to boiling which seemed to help somewhat.

1. A/B/C/D/E.....tested! The parts suspending the screws to be anodized now tinge, but NEVER the screw. Tested: a). Various ph levels, amps, bath times & contact methods. I check for continuity however the screws are very light and float when immersed. I'm now suspending them, "sandwiched" between aluminum screening.

2. PRE-CLEANING wearing gloves with: a). steel wool, b). Scotchbrite, c). dish soap, d). degreaser in that order. I've also tried soaking in vinegar & rubbing alcohol.

For my use surface-dying is acceptable, however I would prefer the deeper anodized colors. I think my problem is either the amount of alloy or a coating. Any more suggestions?

bill

7/25/2014 11:26:00 pm

I am using your technique for anodizing and when i have success it is a very nice job but my problem seems to be keeping electrical contact with the part in the anodizing bath 3 out of 4 attempts will fail I can usually tell now by the amount of bubbles on my cathode. I am anodizing very small parts and I use aluminum wire and titanium wire to suspend my parts with equal failures its almost like they start out with good connection and loose it while in the anodizing process I started using a very small dc transformer 12 vdc 2 amp thinking that maybe my voltage was too low i switched to a 24 vdc 7 amp transformer i have had better luck with the larger transformer but i still have lots of failures can someone please help me with a better method than wraping a wire around or maybe what i need to change to keep contact with the wire while anodizing thanks

Ken

7/26/2014 09:40:52 am

Hi Nancy and Bill,
I have been thinking about both of your respective problems and I woke up at 3 AM this morning with a terrible realization! I have advocated the use of aluminum mesh screening to hold small parts but suddenly remembered that aluminum, as it is anodized, loses conductivity. So, what appears as a loose connection many simply be an increase in resistance causing what appears as a bad connection. Bill, in your case a stainless basket may help or other non-anodizable metal screen.
Nancy, are the parts the same as you had initially with the good result shown in the photo that you provided? Or did the dye wash off of these as well? Your guess about the alloy or a coating may be spot on. Have you tried just anodizing just some scrap aluminum of a piece of 6061 from most hardware stores? Or even, aluminum screws. It seems that you are doing everything right so we can fix the problem! Anodizing is and art as well as a science so hang in there. Ken..

Nancy

7/26/2014 10:28:45 am

Hi Ken,

Yes ... you're right. I'm sorry you woke at 3am! The screen "basket" worked beautifully (although I didn't boil), yesterday. Today, the anodize bath dissolved the screen, loosing contact. I'm back to a previous "holding" method of drilling a hole in aluminum, threading the screw post through it, although not ideal.

Today's test with the screening, the piece holding the screw colored beautifully -- the screw was completely void of any color.
So, I ordered different screws made in the US (no doubt the previous were imports). I'll let you know next week how the new screws work as I'm convinced inferior aluminum-alloy content is my problem - a great A/B test (same everything other than old screws vs. new).

The parts in the photo (previous color question) were not boiled (sealed). The color question is on the back burner until I get the process resolved.

QUESTION 1: " .... a stainless basket may help or other non-anodizable metal screen. ..." Does a non-anodizable metal in the anodize bath create problems with amp current? I'd tried that but the amps were significantly higher than with aluminum only. Also, I had problems with metal corrosion/contact.

QUESTION 2: We can re-use the same aluminum for the cathode/anode if cleaned between uses with lye etch, right?

This has certainly been an exercise in patience!!! Thanks again, Ken for all your help & interest.

Ken

7/28/2014 08:33:26 am

Hey Nancy,
The issue of the anode basket composition is sometimes problematic. Since the environment is acidic, many metals will corrode/lose conductivity. The stainless steel is dependent on the quality of the material. The increase of chromium,(that makes stainless steel more resistant) does have lower inherent conductivity but better resistance to corrosion. However, if aluminum is working for you don't bother considering stainless. And yes, the aluminum anode and cathode are reusable until consumed. I hope to hear from you next week with the "GREAT" results, LOL.Ken.

Nancy

8/11/2014 04:02:46 am

Hi Ken,

Thank you for you continued encouragement. Good news! I think I've got this ... sort of. I'm not sure if I'm completely "anodizing", however I've successfully "dyed" 200 screws fairly consistently in 5 colors: red, orange, green, light blue & light plum. Though, I am not boiling (see Notes #4 below), instead natural dry, bake & acrylic seal, which for my purpose is sufficient.

NOTES:
1. DC POWER SUPPLY: The variable DC power supply was absolutely essential in documenting test results. Using 5.2As as reference, 60 minutes in bath. The voltage [4V to 12V] varies depending on the amount of aluminum being anodized.
2. FAN: I've added a fan to cool the bath solution.
3. PH: I purchased a digital PH meter. Using your recommended bath ratio [2.5 TBL pool chem | 2/3 C distilled water], the calibrated meter tested the solution at .2 which I've used as a reference point. I noticed one batch was "pale". I tested the PH in the bath finding it was at .9. I added more pool chem to lower the PH which corrected the next batch results.
4. TEST SCREWS: I tested screws from 3 different manufacturers in same "batch." None ever showed a "yellow tinge", however the aluminum suspending them in the bath did, so I concluded either alloy content and/or finishing process was the probable cause, abandoning effort to achieve "yellow tinge" & boiling.
- SCREW #1 (import): Satin finish never changed appearance either after lye etch (1-3 minutes) or anodize bath (60 minutes). Finish only changed to dark grey after in lye bath for extended period. RESULTS: Colored well, however slightly paler than Screw #2.
- SCREW #2 (import): Satin finish changed to greyish-silver in lye etch (1:30-2 minutes). No change in anodize bath. RESULTS: Best, colored well.
- SCREW #3 (made in USA): Shiny finish changed to dark grey in lye etch (1-2 minutes). No change in anodize bath. RESULTS: Poor. Dark, dull "gray" under dye color.
5. DYES: Using RIT liquid dyes. I had a lot of difficulty with dark blue so instead, I mixed green & yellow which worked well. If the anodized pieces are not rinsed well after the anodize bath, it caused the darker dyes to turn black. The amount of time in the dyes varied [minutes: 3 (for pale) - 60 (for intense)] depending on preferred results.

I found this article to be especially helpful for pre-cleaning advice:
http://www.precisioncleaning.com/pdf_documents_metal_cleaning/Cleaning%20Times%20Cleaning%20of%20aluminum%20Harvey%20in%20North%20Dakota%20writes.pdf

Overall, I'm very pleased with the results. This is not for the "faint of heart" -- the process is definitely an "art" you've noted. I hope this information is helpful to others. - Nancy

Marcus

8/11/2014 01:00:24 am

Hello there!

I have read a lot of these problems to see if they can account for the problems i am having but i couldn't quite find something similar so i was hoping someone out there could help.

I clean my aluminium very well and mix everything how it says but my pieces don't seem to be anodising. When the piece gets put into the sodium bisulfate tank I get a lot of bubble off the cathode which appear to head to the piece I wish to be anodised however the piece never gets a yellowish tint even when left for up to 2 hours and then doesn't hold the dye when put in boiling water. I know it was said earlier that not all aluminium will turn a yellowish colour but then it doesn't hold the dye anyway.

I was hoping some of you might have a helping hand, well idea, that could suggest an answer.

Thanks a lot
Marcus

Adam G.

8/11/2014 01:25:06 am

What aluminum alloy are you trying to anodize?
What is your cathode made from?

Did you give it a soak in the sodium hydroxide solution before rinsing and going into the sodium bisulfate solution?
What solution concentrations are you using?
What dye are you using?
Size of the item, tank size, cathode size, and power supply??

I don't think I ever saw the yellow tint on items I anodized. Of course I was anodizing 7075 and 6061 aluminum. I know there's at least one alloy that simply won't take anodizing very well (if at all).

Marcus

8/12/2014 10:10:04 pm

My cathode is made from the same aluminium I am trying to anodise however I have no idea what alloy it is as it did not say when I bought it.

I do soak the piece to be anodised in the sodium hydroxide first for a couple of minutes before putting it into the sodium bisulfate solution, as for the solutions I use the same 2% and 20-30% suggested here and I have tried using inks, dylon dye and rit powder dye however they all come off in the boiling water.

I am only doing very small test pieces at the moment, about 10mm x 30mm x 1mm and my cathode is about twice this size.

I am using a rechargeable 6v battery which has been fully charged each time I have tried this process. The 'tank' size is very small at 150ml.

I was thinking maybe I needed a bigger tank or perhaps a proper colouring ink however I guess that maybe the aluminium could just be unable to be anodised?

Hanan

8/11/2014 03:30:22 am

couldn't this just be a simple case of wires crossed. isn't the part supposed to bubble?

Adam G.

8/11/2014 08:29:50 am

I would hope that the person followed the easy instructions above... Positive to the item being anodized (anode) with negative to the cathode setup. I would normally see bubbles coming from both items when anodizing. After a short amount of time, the items in the tank would be obscured by bubbles.

Adam G.

8/12/2014 11:51:46 pm

Marcus,

I would test with an alloy that is KNOWN to anodize and dye properly first. Use either 6061 or 6063 aluminum for the cathode.

I would also move to a 12V battery and connect a charger to it while you're anodizing (the battery provides load to the charger, so you get the power to the tank).

You can also do a test with the pieces once you've processed them, using a multi-meter. Test to see if the piece is still conductive with the meter. If it is, you're not anodizing.

Marcus

8/13/2014 06:46:21 am

Thank you for the advice i shall give this a go hopefully, however finding a certain grade of aluminium is proving difficult as none of the places i have been to know what grade their aluminium is which is a little annoying, it is just sold as aluminium. But hopefully i shall find some and get some results!

Adam G.

8/15/2014 01:31:07 am

Marcus,
IME you can usually find out what alloy the parts are made from. If you're making the parts yourself, then you really should know what the alloy is. Most pieces of aluminum will have the alloy marked right on it (at least those I've bought do). Even at scrap yards, you can get pieces that still have this information on it. Or get the testing equipment to see what the alloy is. If you're doing this as a business that is. If it's just for personal use, it's probably far cheaper to just get the parts in a known alloy.

You can still do a test with a known alloy to make sure the setup is good. Also, when soaking in the sodium hydroxide, the items should turn dark grey. If not, then they've not been treated fully yet (the old stuff eaten off). That could be part of the issue you're having. The parts should be obscured by bubbles while the etching is going on too.

Curious to know if you're using weight measure for the dry chemicals, or volume measure.

Vince

8/14/2014 11:12:35 pm

Hi,

How do control the current? Or, is it just drawing the full potential of the battery? I have a lab power supply. Can I set it for the desired max. current draw and just let it run?

Thanks,

Vince

Adam G.

8/15/2014 01:23:52 am

With the lab power supply, figure out how many amps you need first. Then set the voltage to 12v, and increase the current until you're in the range you need for amps. Depending on your tank configuration you might push more voltage into the system in order to get the current you need.

IME, you're ok with a bit more current and voltage at the start. Mostly due to how you'll have current drop as the pieces get anodized. Do some test pieces to see how long it takes to get a solid layer on them.

Matt C.

9/1/2014 10:48:16 am

I finally got this working - it took a few tries.

I was anodizing some small aluminum brackets I made from flat stock purchased from Home Depot (Everbilt house brand).

I used a piece of the flat stock as the cathode and the bracket as the anode, and then used Dylon Velvet Black clothing dye I sourced from Joann Fabrics. I also sourced some 18 gauge aluminum wire ("Ook" brand) at the craft store (near the picture naming hardware). I followed the cleaning steps (lye) and prepared my acidic solution with distilled water as per these instructions. I used a 12V battery charger at 12A (!) for 2+ hours. I really didn't see a yellow color, but took the part out after that much time. No luck in getting the dye to work.

I decided I needed to more closely follow the instructions, so I sourced a small sheet of lead for my cathode and aluminum stock of a known alloy (6061) from McMaster-Carr. Amazingly, I ordered on a Sunday and it arrived the next day! I then read online the challenges of getting black to work, so I broke down and bought the 4 oz. bottle of black dye from Caswell at $40 (this proved to be a good move).

I cut a big "L" using some tin snips from my sheet of lead. I then carefully bent it (with gloves! lead is poisonous) into a round shape and inserted it into my anodizing cell, which was just a recycled pickle jar. I also decided to use the Caswell 720 calculator to find out that I didn't need to use 12V @ 12A, but rather 0.25A for two hours. I have a bench top DC power supply capable of constant current supply, so I substituted that as well.

Nonetheless, my first attempt with the better materials failed. On another DIY anodizing web site I noted that the electrical connection is critical. My bracket has a hole drilled into it, so I decided to make my connection there. I folded the wire back and forth to make a thick bunch that I forced into the hole. I had to bend a few more sections of wire so that the connection was very tight. I then anodized. After 2 hours I rinsed in distilled water. I mixed a small amount of Caswell black dye and distilled water in the right ratio and heated it with my microwave until it was 140F as measured with my infrared thermometer. The dye took in about 2 - 3 minutes! I kept it in the dye for about 10 minutes then rinsed in distilled water. Finally I boiled it in distilled water for 20 minutes to seal. It worked!

I later substituted my 6061 alloy with the Home Depot (Everbilt) stock and was able to anodize and dye that too!

I haven't gone back to find out if I could get the aluminum cathode to work. I did try a couple pieces of the Everbilt aluminum in the Dylon Velvet Black, but I just couldn't get that dye to take. After dipping in the Dylon, I tried dipping into the Caswell dye, but that didn't work. I really didn't try too hard.

So, for me the key was to make sure I had a solid, solid, solid electrical connection to the piece and to use the Caswell black dye. Also, I think the other key is that the item should be finished smooth after the steel wool/Scotch Brite cleaning steps, since the dying won't hide any surface imperfections. A lead cathode and a DC power supply probably helped.

Ken

9/2/2014 08:55:13 am

Hey Matt,
Thanks for the great post with all of the details so well spelled out. You covered two of the key factors with any anodizing even with H2SO4: Good electrical connection to both the anode and cathode. And, proper surface preparation. As the anode piece proceeds it is being passivated (less conductive) and the resistance goes up requiring more current. I have found that aluminum alligator clips work well if you move them several times during the process. And, you are correct that dye will not fix imperfections! As far as the cathode is concerned, I see no reason why aluminum will not be as good or better and safer than lead. I have used both and find no discernible difference. Again, thanks for the excellent post, Ken.

Hanan

9/15/2014 05:28:40 am

I've just about had it. I start out by tumbling my parts in glass beads. I then empty the tumbler of glass beads and run in detergent water. Then I rack the parts. rack is made of titanium wires and load center grounding strip. Parts racked in there have zero resistance to main lead. Then I dunk the rack in acetone and alcohol. "Dunk in tap water and then rinse spray with distilled". Then go for a 3 min etch in lye solution again " Dunk & Rinse" Then in the deoxide/desmut from Caswells at 100F "D&R" again. finally in the anodizing tub which is @ 1.1pH and voltage as per 720 rule with constant current switching power supply. Now the weird thing is that after 3 minutes @ 1.5 amp 15 VDC, the read go to 31VDC ( as far as it will go) and .8amps. Bubbles are coming out of the parts too instead of the cathode. I am using aquarium pump for agitation. All the while I have verified my cathode and every wire with continuity tester. 2 hrs later pull out parts "D&R" and then in 120 F RIT dye for 40 minutes. Well after 10 minutes in dye parts look black. Then when 40 minutes was up I rinsed em all with distilled cause if I dunk em too long dye runs out. Then when I steam them in 212F water all the dye runs out leaving only a few spots of black and the rest of the part yellowish gold. Where am I going wrong? I am 100% certain that I am not touching the parts throughout the process once they are racked. I am about to move to sulfuric acid, and caswells dye but I doubt that will solve my problems. BTW, some of my part are not 100% insulated, they have a few spots of continuity here and there.

I really need teh help cause I am about to lose my mind. Thsi ismy 6th time failing at anodizing. I only had one successful try and that was 1 year ago without PH meter or digital scale or grounding strip for connection and I only was using reverse osmosed water.

Ken

9/15/2014 09:10:14 am

Hello Hanan,
I understand your frustration but lets look at what may be happening and what appears certain. First, if the aluminum will not take any dye it is not anodized. It may be oxidized or passivated but it is not forming any cell structure. The fact that there are no bubbles at the cathode says that there is no surface activity. Consider the use of titanium as a possible culprit. I have used titanium but found that most of the problem with its use is the fact that it is a transition metal with only a 10 % of the conductivity of a consumable like aluminum. And, as it is a great corrosion resistant metal, the resistance increases as it becomes passivated. It is a tough problem to solve and the only reasonable answer seems to be an increased cross-section, which may not be possible due to cost. But, the same problem exists with H2SO4. Another question to answer is whether or not the aluminum is alloyed with a problem material like silicon. I would suggest that you try a small experiment and just try to anodize a part with aluminum wire and aluminum cathode after etching to test the process. pH looks good. And, as a long tern project I have always suggested a good dye like Caswell but RIT should prove if the process works for you. Let us know what happens and we will solve the problem. Ken.

Hanan

9/15/2014 09:37:23 am

So the fact that I have very very low conductivity isn't saying much. BTW I did a few parts with aluminum wire and teh results weren't that much better. I will change my cathode to pure aluminum. I'll etch it and if it stays white I know I have a 6000 series aluminum plate. I've already sunk so much into chems and PS and racking etc etc. I feel like one of those automotive hacks that is just throwing parts at problems. I mean after all, the pros are using titanium wire. Give me a resistance reading to verify that I should get rid of the titanium and if I surpass that I will quit titanium.

Jeremy

9/15/2014 10:03:44 am

Titanium wire is not your problem. I have successfully used Ken's process with titanium wire. What grade aluminum are your parts and cathode? Also, I have successfully used this process using aluminum foil as a cathode.

Ken

9/16/2014 08:22:29 am

Hanan,
Jeremy is right that titanium is fine to use but I was suggesting that it simply is less conductive than aluminum. I can't give you the resistance because that depends on the voltage and current used which are variable and the quality of the electrolyte. I can't measure them from here. One thing that bothers me is that you said in your first post that there were no hydrogen bubbles at the cathode which says that there is no contact, insufficient voltage or current, or contaminated electrolyte. Take two pieces of small aluminum and a small amount of electrolyte and use a D battery to test the electrolyte. This is a simple process and does not require throwing lots of parts and pieces at the problem. It is however an art as much as a science so don't get discouraged. Ken.

Hanan

9/16/2014 09:16:56 am

OK regarding Ti wires, would you think it any different if I told you that I have a CC CV power supply? This leads me to ask, could I just set the PS to CV 1.5 V and use two aluminum fence wires and test my electrolyte like that? I am suspecting weak or contaminated electrolyte. The parts that seemed to anodize now seem like they are all corroded. I dunked them in lye in order to stop all the salts from forming on their surfaces. Last night I wiped the parts this morning more salt. Then I dunked the parts in just enough distilled to dissolve those salts on the parts and I came up with a pH in that soln of 8 pH.
Thanks for all the help, its really helpful.

Ken

9/17/2014 01:52:55 am

Hanan,
Yes, constant voltage between 1.5 and 6 volts will determine the quality of the electrolyte. Use small amounts and make a new solution to test vs. the current one that does not work. Should be informative. Ken.

Hanan

9/17/2014 06:57:40 am

Should I keep the amperage below 3 amps?

Adam G

9/17/2014 07:07:51 am

I've had best results using the constant current model. I set the power supply to 12v +/-, and the amperage/current to what's needed to do the job. The power supply modulates the voltage to ensure it provides the same current for the process. It's been documented that the constant current model is superior to constant voltage.

I would also check to see how many Ohm of resistance your tank/solution gives. That will also determine how effective the anodizing is. I had difficulty when I went to a larger tank, with more solution in it, which produced more resistance.

As already mentioned, make sure you use known alloys of aluminum for the cathode. It also helps to know what the anode (piece to be anodized) is made from. I've had good results with 6061 for the cathode and either 6061 or 7075 for the anode. I also use aluminum wire to make the connection to the anode. I force it into a tapped hole, as tight as possible so that it makes solid contact. So tight that I have to hold the wire (folded onto itself several times) with Vise Grips to get it threaded in. For the hanging wire, I just bought some from Home Depot. It's the 2/2/2 main service line wire (thick bastard) bundle.

Another thing I've had best results with is using all the solution cold/room temp. I also use deionized water to rinse, and mix up the solutions. make sure you're at least within the range of chemical concentration for the etch and anodize baths. If you're not having good results, try in the middle of the range, or even the top end of the range. ALWAYS measure the powder chemicals by weight. While it might not seem like a big deal, accuracy is important. Volume measure of dry ingredients is notoriously inaccurate.

Hanan

9/17/2014 09:39:41 am

What does it matter how much electrolyte I have in my bath as long as I only have a short distance between the parts and cathode? I am talking like 1.5-2.5 inches. My resistance of the electrolyte is 3.6Kohm. Put the leads in and started at .6Kohm and within a minute that reading was arrived at. At that point the rate in which the reading was increasing was exponentially slower than when I put the leads in. Regarding that 1.5 volt test, I used aluminum wire 1" apart and no bubbles, only after reaching 24V did the -- side show bubbles. Will make up some soln and test that.

Hanan

9/18/2014 09:35:56 am

My existing electrolyte showed no bubbling while the fresh sample 40 Gram to 160mL gave me a lot of bubbling at 1.5V CC. I guess I will make up some electrolyte and find a better way to store ( I guess I'll pay for a 5 gallon bucket and cover) it when not in use? I guess I'll also be buying some 1/16-3/32 6061 to put on the side of the bucket as cathode. Anybody have anything to add about my observations?

Hanan

9/18/2014 09:40:17 am

BTW, only the cathode showed bubbling. If the anodized pc is being eroded, is that a sign of too much amperage? The heat was definitely going up after I hit 1 amp ( took 18VDC to push that much amps). My surface area was .157"

Adam G

9/18/2014 09:44:28 am

Are you sure you have the "+" and "-" set to the correct pieces? Your anode should not be getting eroded during the process. If anything, you'll get build-up on the anode.

Hanan

9/18/2014 09:51:53 am

I just stuck 2 aluminum wires in a cup of acid water and the + side got shiny and started eroding into a tooth pick form. This was just an experiment to see what should be going on in perfect conditions.

Alex K

9/21/2014 12:39:53 pm

Hi Ken,
great article. I am curios if you could potentially give me some pointers. I am building a little gizmo which involves a 1 ft long 1 inch aluminum rod that will be used with heating/cooling of food. From what I researched, hard coat anodized aluminium should be used (as in black cookware etc). Supposedly the hard coat is considered food grade.
I have never anodized anything. Do you think i would be able to use your technique on a slightly larger scale and simply keep the aluminum rod in the solution until it turns dark grey/black to indicate a thick layer of aluminum oxide? Would you suggest dyeing the aluminum with a food grade dye or simply leave it as the dye wouldn't be accepted easily do the smaller pore size with hard coat anodized aluminium?
Any thoughts would be appreciated. Thank you so much for your writeup.
Alex

Ken

9/22/2014 03:39:20 am

Hi Alex K.,
Your question is a bit more complicated as the FDA does not have a consistent regulation about food safe anodizing. But here is my thought process: All aluminum naturally oxidizes to form Al2O3 which is a protective layer. Food and bake ware ( un-anodized) have been used for years for food contact and are only really discolored in acidic conditions or in dishwashers with caustic cleaners. The hard coat (type III) anodizing requires more stringent control such as cold temperature (32F) and higher voltage and current. And, any problem with anodizing for food seems to be the dye leaching out. The best guess that I have is that you could anodize with my process with just the yellow hue and seal with boiling water. It will possibly be more resistant to wear. I am sorry that I can't be more specific but it is a tricky question. Thanks for the question and comment, Ken.

Adam G

9/22/2014 04:28:00 am

Alex, as Ken has already mentioned, Type III hard anodizing is a very different animal. It also requires additional hardware to keep the solution cooled to the correct level/range. Plus a different power supply is needed. From my earlier research it's higher volts at amps than we're using. Essentially, we can get up to Type II anodizing at the home/DIY level without a major investment.

Have you considered going to stainless steel instead of aluminum for your gizmo? Or even copper. I believe copper is a better thermal conductor than aluminum is. That being said, I get excellent results with my plate chiller, that's all stainless inside (for chilling wort when making beer). Most/all RIMS systems I've seen (for heating for the mash process) are stainless housings with electric elements. I believe the HERMS system passes the solution to be temperature changed through stainless tubing inside a vessel where water is heated to the desired temperature (or adjusted to make sure it's the right temp when it goes back into the target vessel).

Personally, I wouldn't try to anodize anything that will be in direct contact with food. At least, not until I can attain Type III hard anodizing spec's with my hardware/process.

Alex K

9/22/2014 07:19:11 am

Hi Adam and Ken
Thank you so much for your replies. Just to give you all a bit more context, the gizmo i want to build will cool/warm beer fermentation. I just want to build it as a fun project as I have seen something similar commercially available.
The aluminum rod will be submersed in fermenting beer. In essecence coper would be fine; however, it leaches into the beer due to the lower pH values and is should not be used in the fermentation process. Stainless steel would be fine but its heat transfer capacity is to low to be efficient enough. Aluminum is a compromise and in theory with a healthy layer of Al2O3 should provide enough protection to be submersed in fermenting beer even at lower pH values. Al could be used as a fermentation vessel if it built up a layer of Al2O3 (i.e. through boiling water in it), hence the aluminum rod should not affect the flavor of the beer (hopefully).

I will give Ken's approach a try and anodize it till I get a good discoloration and will boil the rod afterwards to seal it. Should I get any off flavors, I might consider using a food grade paint of sort to seal it even more.. I would agree with Ken that it probably is the dye that would cause problems when in contact with food.
Thanks
Alex

Adam G

9/22/2014 07:22:57 am

Alex,
I treated an aluminum pot to use for brewing before. So I'm fully aware of how that works. I also found it worked best using hot water, for some reason.

Still, if you go the anodizing route, you can test the piece (once done and dry) to make sure it's no longer conductive (multimeter/tester). If you can keep the electrolyte solution chilled, you have a better chance of getting a better result (IME). I had better results doing this in the colder months (winter in New England) than in the warmer months.

Alex K

9/22/2014 10:47:35 am

Hi Adam,
thanks for the hint, I am in a cold part of Canada and am going to give your recommendation a try with chilled solution. Perhaps I can put it in an ice bath of sorts.
Thanks
Alex

Dan W

10/24/2014 07:34:27 pm

Hi there. I'm from Lincoln, England. I'm just experimenting with a bit of DIY anodizing. My results are going OK but I'm trying to improve them all the time. My set-up at the moment is a 12v 3a DC supply. I'm using glass containers for the anodizing container and am using Sodium Bisulphate (minimum 92% pure) in a mixing ratio of 20% SB to 80% distilled water. I'm using lead flashing strip as my cathode. I am trying to anodize aluminium plate strips 80mm long by 15mm wide x 1mm thick. The cathode is the same size as the aluminium strips. Ok so im anodizing for about 1.5 hours currently. I'm using RIT dye to dye and I'm sealing with boiling water. All my baths are at room temperature. Like I said I'm achieving results but not brilliant. Any ideas people?

Ken

10/26/2014 02:32:45 am

Hey Dan,
Three possibilities occur to me as I followed your comment. First, I have used lead as a cathode but found that there is great variability in flashing. A simple experiment substituting aluminum might be useful. Second, although 92 % sodium bisulfate should be fine, it is easy to recrystalize for a pure chemical. Distilled water will hold 100 grams @ 100C and only 28 grams @ RT. So crystals will form easily if refrigerated. Third, RIT dye is extremely variable in composition and your results will be better with a dye designed for anodizing like Caswell. I am not sure what is available in Great Britain but it is worth consideration. Additionally, 1 and ½ hours seems like a long time for such a small piece of aluminum. Please keep us informed as you get better results, Thanks, Ken.

Md.Murad Hossain

10/29/2014 07:50:58 pm

Hi, from above instructions i seem before anodizing process etching is done by NaOH solution. Is it necessary to immersed the body to before anodized in HNO3, H2SO4 and H3PO4 solution. For etching which temperature i maintain for 2% NaOH solution. Please give me suggestion. Thanks

Ken

10/31/2014 03:25:21 am

Hi,
After etching in NaOH simply rinse with distilled water and anodize. I am assuming that you meant 20 % sodium bisulfate and if you start at room temperature there will be a slow rise and only experimentation will tell you if if is too warm. Try and test warm vs, cool. Thanks, Ken.

Mike

10/30/2014 09:33:26 am

I am sure that someone has already answered the questions I have but too many posts to read.

I am so far unsuccessful in anodizing. I am not sure of the alloy I have. I purchased a strip of 1/8"x3/4" aluminum for my cathode. I am using a 12v 1500mA wall wart as the power supply.

First try I got some bubbles not not much. Part would not take any dye. I then realized the aluminum I bought for the cathode had a non- conductive coating on it. I used a wire wheel to clean the coating off some of the aluminum that would be in the bath and some where I clip the power supply on.

I put an ammeter in series with the supply voltage and only get about 50mA. Still getting bubbles, but with low amperage I doubt it will anodize. Any suggestions on getting the current up without having to buy an expensive constant current supply?

Ken

10/31/2014 03:41:45 am

Hi Mike,
This sounds a lot like a connection problem with such a low current draw. As pointed out in previous posts a constant current is better than constant voltage. Check the resistance of the solution as high resistance reduces current flow via ohms law. But, please read some of the previous posts as this is covered in detail. Ken.

Mike

11/2/2014 09:31:07 pm

Ken, I have now been successful with anodizing my parts, but my color is very inconsistent. I am trying to anodize four go kart hubs. I am not sure of the type of aluminum, but would"assume" they are the same. am using RIT liquid orange dye and while some of my parts are orange tinge, one is a gold color. I have got the current draw higher, but that seems to still be a variable. Some parts are in the 1A range while the suspect one is in the 600mA range. I know you have mentioned that the caswell dye is better, but before I invest in that dye, I am asking if you feel that is the issue or is it the current. If current, is the only solution the constant current P/S? I am trying to spend as little money as possible. Thanks.

Ken

11/4/2014 07:10:40 am

Mike,
With regard to the power supply the question becomes how much anodizing you plan on doing. If, for the long term you will be doing more, then a CC supply might be worth the cost. Hell, you could even buy a kit and assemble it yourself and save a bundle. As far as the Caswell dye, again, is how often you might use that color. That is a significant cost if it will only be used once or twice. The question of the one hub is one that I see a lot. Many of the aluminum products come from recycled aluminum and the composition is variable. But, that one hub seems to be perhaps something else. Could it be coated? What happens if you re-etch and re-anodize? Best of luck, Ken.

ste

11/18/2014 01:42:42 pm

Hope someone can help done all the above my aluminium motocross nipple when nice and yellow so put them in the dye funny enough only one was anodized nice and gold not sure if I missed something! But looking at them thers loads off bronze patches

Ken

11/20/2014 01:04:30 am

Ste,
My best guess is that there was contamination introduced during preparation. For example, if emery cloth is used it can leave metal behind to cause problems. If it was properly cleaned and processed then variability in material composition may be the issue. But, where one was fine, the cleaning seems to be the problem. Ken.

ste

11/20/2014 01:18:11 am

Hello ken thanks for the fast reply I was think about the cleaning probs never got all the crap off the parts the one that anodized wasn't not a shinny as I wanted goin to repolish the parts and try again also is there anything else I can use insted off aluminium wire like copper wire or something regards ste

Ken

11/20/2014 07:40:52 am

Ste,
I recommend mild etching with sodium hydroxide (lye) at 2 % but if you prefer an abrasive I would suggest a non-metal abrasive like Scotch-Brite, (here in the US). But, there should be something similar in the UK. There are sponges sold in markets with one abrasive side and this will work. Ken.

ste

11/20/2014 08:11:20 am

I done the 2% come out sparkling also polished them befor hand forgot to mention I used a copper wire to hold the nipples would that effect the anodizing thanks ste

Joseph Chance Watkins

11/26/2014 11:30:03 am

Thanks for sharing this method with us; Jesus Christ Bless you! :)

Brian P link

1/10/2015 09:32:10 am

I plan on doing some motorcycle parts. If I bead blast with glass, would that be advisable? or is there a better way to clean out all the hard to reach areas?

hanan

1/10/2015 09:55:09 pm

If you have blasted other materials with other medias in a blasting cabinet and using that. Clean it out extra clean. NO dust no remnants no nothing in the tubes. then put you beads in there and bring down the PSI to about 30-50. Find exactly what setting works for you. Then you will have to do the degrease, rinse, NaOh, rinse and deox/desmut, then rinse. You want to make sure there is no way you have AloX on there before anodizing.

Adam G.

1/10/2015 11:22:10 pm

Glass bead blasting is NOT recommended for use on aluminum. The beads can/will break and embed into the aluminum. Better to use either aluminum oxide or coal slag media (at least 100/120 grit). Coal slag can be found at most Tractor Supply stores, easily. It's also damned cheap to buy (about $8/50# bag).

I would degrease any motorcycle parts with an acetone soak (at least 5 minutes, 10+ being better) before blasting them. You'll still want to soak in sodium hydroxide.

Personally, I'd just skip over the blasting step in this case. Degrease fully, soak in sodium hydroxide to etch, then continue on as normal.

Ken

1/11/2015 12:58:06 am

Hey Brian,
I agree with Adam G on this one for the same reasons. Blasting would be risky and redundant and not really accomplish what you want as a finish. Unless you want a "pitted surface" I would go with NaOH treatment alone. Let us know how you do anodize these parts. Thanks, Ken.

SL Graham link

1/17/2015 05:14:30 am

Hello, wanting to dye sheets of aluminum and then use as a painting surface. for the dye. I have purchased some aluminum as anodized aluminum that came sealed from the environment so not worried about that but dye did not take. I contacted the supplier but was told they did not know about dyeing. So-o- want to try and anodize my own aluminum to dye. What type of aluminum sheets should I start with? Suggestions.. I am new to this...have played with dyeing aluminum and loved the artistic possibilities.

Ken

1/18/2015 12:36:59 am

Hello and welcome,
The two primary concerns in choosing aluminum are the composition (What alloy), and whether or not the sheet is sealed with something other than the natural oxide layer. For example, the 1000 series is the best to anodize as there is virtually no other metal present. The most common and still a good choice is the 6061. As the amount of alloy (frequently copper) goes up in the 3000 range, anodizing becomes less predictable. Here is a link to copy and paste that really covers the choice of aluminum. Scroll down to the section on dyeing and I think that it may be helpful. Thanks for the question and stay in touch, Ken
http://www.omwcorp.com/understandingano/anoindex.html

Joseph

1/24/2015 04:38:38 am

Hi Ken,

Thanks so much for such a great and interesting article :-)

I don't know if this question has been answered before, I would like to learn how to make anodized name plates (aluminium data plates), on the world wide web there does not seem to be much information as to the complete step by step process of making anodized name plates, such how they are printed on to the anodized aluminium plate before the sealing process, I did find one very interesting video on youtube of a special laser marker making such a name plate see this link: https://www.youtube.com/watch?v=8EnUgIURiVA

This seems to be a cool, modern method of producing name plates! but I know that anodized aluminium name plates have been around probably since the 1940's or 1950's and first laser was only invented in May 1960 and there were no sophisticated CNC computer systems back then! in the 1940's / 1950's so how exactly were the early anodized name plates made ?

Joseph

1/31/2015 05:54:35 am

After a whole week searching about "how the earliest anodised aluminium nameplates were made ?", I came across this website:-

http://www.horizonsisg.com/metalphoto.html

It shows various nameplates and describes the original process of how they are made using a special type of photo sensitive anodised aluminium plate/sheet, they call it "Metal Photo" and it was originally developed in 1950 by a company called Horizons Research Incorporated.

There is also a Wikipedia article about photo sensitive anodised aluminium at the link below:-

http://en.wikipedia.org/wiki/Photosensitive_Anodized_Aluminum

Hope this information helps others.

Ken

2/1/2015 12:48:15 am

Hi Joseph,
I have actually used these some years ago and had forgotten this interesting technology. They have stood the test of time. Thanks for the information and expanding our shared knowledge. Ken.

Joseph

2/5/2015 04:32:06 pm

Hi Ken, You are most welcome, Glad I reminded you of this amazing technology you used to do!

All the best, Joseph.

William link

2/21/2015 12:23:23 pm

I have been doing various online searches and reading the blogs. I am new to anodizing, so am wondering about my situation. I purchased a 6" X 12" aluminum heat sink for a project I am doing. The heat sink also has 2 " fins that run the 12" length. I have read that anodizing the aluminum a flat black will make it more efficient in giving off heat. I have a 10 amp, 12 volt battery charger that I have added a sufficient amount of capacitance to the output which helps it be more DC in nature and hopefully higher in voltage.
My obvious question is, what grade of aluminum do heat sinks use? Will using the battery charger provide enough current to at least obtain some black anodizing for the size piece I am wanting to anodize? With all of the fins on top of the actual piece size, that is a lot of square inches. If the current is not sufficient for the amount of square inches involved, could I possibly allow more time be the offset factor? I will be using a mixture of battery electrolyte and distilled water. Any insight as to the type of aluminum I am most likely dealing with and the other issues would be greatly appreciated. Of course, the aluminum will be properly prepped and etched ahead of time. Thank in advance.

Rod

3/2/2015 09:05:46 pm

Where did you purchase the heat sink from? I would suspect if you contact them they could tell you what series of Aluminium it was machined from. One of the issues you will run into is getting the process to grow the Anodize Layer down into the valleys of the fins.

The process is somewhat line of sight from the anode to the cahtodes. You will need to setup multiple or one very large flat electrode on both of the large surface areas to accoumplish this.

William

3/3/2015 12:40:46 am

Rod, I purchased the heat sink off of ebay. It was used, so have no information regarding where it was manufactured. From my research, it seems that most extruded heat sinks use either the 6061 alloy or the 6063-T5 alloy. More than likely, the heat sink I have is probably the 6061 alloy (best guess). The heat sink does not appear to be a custom sink, such as using 6061 for the base or pan, and using something like 1100 for the fins which would be brazed to the base. It's just one piece of extruded aluminum.

I read some information from one of the commercial anodizing companies that it is best to keep the area of the cathode 1/3 the area of the aluminum to be anodized. Trying to find the site again to publish the link. Have to figure out the heat sink area precisely, but it appears to have a total area of roughly 5 square feet. I was looking for some lead used in lead flashing for the cathode, but no luck so far, as anything new comes in rolls which is way more than I need (and too pricey as well). So, for multiple cathodes, you simply space them around the sink? Would that make for a more uniform layer of anodizing on the sink? This is where I need to pick someone's brain, since I am not using a large tub, but one that is about twice the size and depth as the heat sink. Not sure if one cathode or several cathodes would produce different results.

William

3/3/2015 12:49:13 am

Just remembered something else to ask. Has anyone ever drained a used wet cell battery to use the electrolyte? Just wondering, as I have a wet cell car battery that is not that old, but has a shorted cell. I thought about draining the electrolyte and taking the battery apart, using the lead plate material for my cathode. I would clean the plates well before using them. Any thoughts? I'm sure the battery is heavily sulfated by now, so not sure about using the electrolyte. But, what about using the lead battery plates for the cathode?

Jose E

4/30/2015 04:18:11 am

Here´s a video that we made for school about the process, you can also see the finished result against the original. https://www.youtube.com/watch?v=SAKLCvEXRyc&feature=youtu.be

William

4/30/2015 04:31:09 am

Interesting video. I must do some more research regarding the temperatures involved. Two things I would do differently, however, regarding the video.

1. Wear the proper gloves when dealing with caustic chemicals and acid.

2. Wear the proper goggles.

SAFETY FIRST!!!

Tony Russell

6/16/2015 08:28:32 am

About black dyes: black is often made up of a mixture of red, blue, maybe yellow dyes. If a mixed black dye is used for dying Al, the color that has the greatest affinity for the Al oxide will be the one that binds, so don't be surprised if you get a color you weren't expecting.

You can test your black dye by putting a small spot on a piece of paper towel, then put a drop of water beside the dye spot so that it seeps into the spot and carries the dye with it. If the dye is composed of several colors, they may start to separate as the water seeps further. This process is called "paper chromatography."

If you want to get Al black, look on the Internet for blackening chemicals. They are not dyes, but react with the Al to form a black coating.

Laci Tele

8/27/2015 09:33:25 am

All of the anodising tutorials forget about some really important practical tips.

For example :
The workpiece must be the anode, this is why its anodising. But.
How do you fix the wire to the workpiece ?
Imagine a cube with flat sides, what you want to anodise, all sides of it. Croco clips may scratch the surface, flat things may cover the surface (or part of it, then it won't be homogeneous) . How do you fix the wire to it ?

If you have a long workpiece, a 30'' long shaft , with 1'' diameter.
How do you fix the wire to it, and what kind of cathode will you use ? It must be long also ?

No one talks about these important details.

Ken

8/27/2015 10:49:49 am

Hi Laci,
You are correct that we sometimes make assumptions that rely on an intuitive experimenter. We perhaps expect that the solutions seem clear but this is not true for everyone. However, It was made clear in the write up that the anode was the positive and that the cathode is negative and has to be at least as big as the piece to be anodized. "Attach the negative battery lead to the cathode which should be at least as large as the piece being anodized. Attach the positive lead to the piece to be anodized. Picture at end of post". The question of anodizing irregular shapes successfully is covered in multiple comments but I should have covered it in the post. For the cube and the rod simply make a cradle or basket of aluminum wire that holds the item submerged and extend part of the basket out of the electrolyte. The item can be rotated periodically and the anodizing will be uniform since the time is relatively long. But, I appreciate you comment as I am working on a YouTube video and will cover these points more completely. Thanks, Ken.

Hanan

8/28/2015 07:12:55 am

Laci, if you were to familiarize yourself with professional anodizing racks, you would notice that those sharp titanium fingers are like that for a reason. They literally bite into the workpiece in a very small area. Some bite inside a hole or pocket and some from the outside.

patrick k

8/28/2015 09:24:31 am

Hi ken
At the beginning you stated that there are a few types of anodizing and that one is for strength and this method is for dying.is there a processto do both? If not directly then should the dye process be done first then the strength process or vise versus? Thanks in advance for any thoughts on this.

Ken

8/29/2015 03:48:03 am

Hi Patrick,
There is actually no need to do both as resistance is related to pore size. With this process the pore size is small and the protection is excellent if it is sealed in boiling water. However, for a better understanding it would help to go to the link on electrochemistry at the bottom of the video. There is a lot to learn about anodizing and I am still learning as well. The Wikipedia article is also a good source if you go to the sulfuric acid section which discusses type II and type III. https://en.wikipedia.org/wiki/Anodizing. Best of luck in the process, Ken.

Dave Burrows

9/3/2015 05:24:01 am

I'm making something that requires that a lot of small rods and tubes (2mm to 10mm in diameter x 10cm to 35cm long) be anodized. I'm considering the possibility of attaching each to a wire, and those, in turn, to an electrical service entrance type bus that's suspended over the bath, but I'm concerned about marks where two might accidentally touch. I'm also thinking about some sort of electrically conductive tumbler apparatus in which the drum is perforated, and rotates in the bath. I've seen some contraptions that work on this principal on YouTube on an industrial level, but I'm not understanding the electrical aspects of this idea. Does the entire drum behave as the anode? Have you tried anodizing many small parts at once?

Hanan

9/3/2015 02:32:35 pm

Keep in mind anodized layer is not conductive. so as the parts are tumbling around and if any of it manages to anodize those anodized spots won't be conductive and you won't get decent coverage. you need a good connection for this to work.

Ken

9/4/2015 09:23:27 am

Hey Dave and Hanan,
I have anodized small parts using homemade baskets made of aluminum wire that is easy to obtain. Simply shake the parts periodically and they will anodize completely. And Hanan is correct that anodized aluminum is less conductive but it is easy to clean the basket in the 2% Sodium Hydroxide solution (Lye) for 5 minutes to strip the anodizing. The better choice would be titanium wire or basket as titanium retains conductivity longer. Professionals use titanium but I still use aluminum and have found cooking utensils with sieve like holes and perforated baskets. Thanks for the question, Ken.

Gina link

9/19/2015 06:02:42 am

Hi Ken
Thankyou for this site, it has been very informative reading the forum. I have a small problem with the quality of my colour. I am using Caswell Dyes. After sealing in boiling water, the surface colour has a sort matte velvety look to it. Almost like there is a coating. Any thoughts?

Ken

9/19/2015 09:33:59 am

Hi Gina,
Before I make some wild guesses I have some questions that may help to narrow the possibilities. Was the piece pre-etched in sodium hydroxide? Was the anodizing solution too warm? Was the dye bath cold or hot? Have you tried to polish the piece and if so what happened to the film? Do you know which alloy it is (6061 or high grade)? My best thought at this point is that the pore size or depth is the problem but the answers to the questions, as best as possible, will help. Good question and thanks, Ken.

Nate

10/21/2015 03:13:37 pm

Hi, Ken! This is a great tutorial, and I'm anxious to give it a go (Amazon is sending me the stuff, now!)

You mentioned using Krylon clear coat or a sharpie to create an etch resist. How well do these work? I'm looking to anodize some aluminum tube, but the inside doesn't need to be etched -- and it'll help reduce surface area. I'm guessing tapes don't work well in the NaOH solution. Would general spray paint work?

Thanks again for this great article!

Ken

10/22/2015 04:10:11 pm

Hi Nate,
If I understand you correctly you want to resist the NaOH and not the anodizing solution. I am a little puzzled as I don't see the problem with mildly etching the interior of the tube. Yes it will reduce the surface area, but the effort may be more work than it is worth. NaOH is pretty aggressive with aluminum and resists are hard to come by. Have you thought about closing up the ends of the tube? Or maybe rolling up some plastic film on the inside? The Krylon spray and Sharpie work well with the anodizing solution but I am not sure about highly basic materials like NaOH. If I did not understand the problem correctly please let me know. Thanks,Ken.

Nate

10/22/2015 05:11:07 pm

Gah. Not sure why I said NaOH. I meant the anodizing solution.

I'd like to be able to keep the amperage down, if possible. Plus, it's already a high surface area that I'm thinking about anodizing, and I don't want to deal with a big cathode piece.

Kevin

11/15/2015 06:08:25 pm

Ken,

I think this is a great write up and I am very interested in doing some DIY anodizing. I have read through everything and was very interested in Jeremy's post from 9/5/2013 and the success that he had. I had origianlly tried using a wall wart that I had laying around and tried it with some random pieces of AL I had laying around to see what would happen. It worked OK, but the dye was not taking very well (I am trying black which I know can be difficult). I thought that maybe it was my dye (I went with the powder stuff instead of the liquid) so I got the liquid. Now I am having getting no dye to "stick" to the parts at all. I don't know if my process is wrong or what.

Next I decided to get a power supply like Jeremy had talked about. Found this one on Amazon and thought I would give it a try.
http://www.amazon.com/gp/product/B00NHDYMG0?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00
I hooked it up and I am getting the same results.

Here are the materials that I am using:
Lye Mixture
3 cups of distilled water and 15 tablespoons of the pH down
RIT Dye solution
Aluminum Wire for Mobile Homes (found it at Lowe's)
Anode and Cathode are 6061 AL

Any suggestions or tips are appreciated. I am trying to figure out what I am doing wrong.

Ken

11/16/2015 04:03:03 pm

Kevin,
While it is difficult ti diagnose at a distance, there may be two problems. But first, are you still using black liquid dye and is it at room temperature or heated? Have you tested the current draw? This is the most apparent cause as aluminum wire becomes an insulator during anodizing. The aluminum wire you used may be marginal in its conductivity. A short piece to the anode is fine but just be aware of the problem. And although the power supply is constant voltage (12 VDC), it may be current limiting. The amounts of water and sodium bisulfate are close to 20 % but check the bottle to see if it is less than 90 %. Some pH down has more other ingredients. Let me know how you do with this so far, Ken.

Robin

11/21/2015 07:51:12 am

Hi, I have an ali tube that has previously been anodised and coloured black. However in use over time the black has been rubbed off in places. I would like to make it black again. Can I go straight to the dying process ? Or would I have to start from scratch ? thanks

Ken

11/21/2015 09:39:01 am

Hi Robin,
The fact that the color is gone means that the micropores are broken and the surface can not accept dye until they are regrown with anodizing. So yes, it is back to square one and it will have to be stripped and re-anodized. But recall that black is the most difficult color to make unless you use a professional dye like Caswell or other similar. Ken.

robin

11/21/2015 09:45:49 am

Ok thanks, so if I use caustic soda to strip. I have some rit dye on way to me, the caswell is too expensive in relation to cost of item.
Do you use salt in with the dye or just use it neat.

cheers

robin

11/25/2015 11:14:45 pm

Ok, did not go as planned.

I stripped the old anodised layer no problem.

Putting on a new layer is where its gone odd.

The tube has gone rough after being in the tank for a couple of hours.
Almost like it has a sandpaper texture built up.

It was smooth after the strip but re-anodizing has gone wrong.
any ideas ?

thanks

robin

11/26/2015 04:15:45 am

Just to add what i put earlier, it looks as though the item i want anodised has continued to be stripped further rather than built up with anodise. Yes it was ph- i used, yes object was on +ve terminal, yes it was bubbling. very confused why this is the case.

Ken

11/26/2015 11:30:42 am

Robin,
My best guess is that when you stripped the tube the dye was removed but left behind micropores that are not easily visible. When re-anodized, the pores became larger but irregular in size. This is the sandpaper effect. I suspect that the tube will have to be buffed or abraded to remove the pores to expose a uniform aluminum surface. To verify the integrity of the surface you can check continuity with a multmeter. If the surface is conductive you have removed the micropores. If not, some anodizing is remaining. I hope that this helps, Ken.

robin

11/26/2015 11:36:03 am

Thanks Ken

Think I need to practise more.

Cheers

Robin...

Comivo

12/12/2015 01:44:37 am

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Thanks and Regards
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Randall link

1/1/2016 08:58:51 am

Ken,

How do you control amps on your circuit with a car charger? Do you wire in a voltage controler?

Ken

1/1/2016 04:08:29 pm

Hi Randall,
Car battery chargers are normally constant voltage chargers with the current controlled by the battery resistance and temperature as well as the chemistry of the electrolyte. There is no absolute requirement to control the current if the electrolyte remains acidic enough and the temperature does not rise to the level of being hot. This causes the anodizing layer to re-dissolve. But, slowly dropping amperage is normal and should not be a problem. Many home anodizers prefer constant current but constant voltage works for many applications. If you want serious control then find or build a CV/CC power supply. Hope this helps, Ken.

Hugh

1/7/2016 09:36:01 pm

This is a great article and I've read all of the questions and responses. I have a question about compatibility for what would be my most-important application of this process, though. Simply put, I need to know how resistant Type II anodizing is to ethanol (E85, specifically). The parts I want to anodize are fuel rails approximately 1/2" inside diameter and 15" long. Flow rate could exceed 6L/min @ 65PSI, under full throttle and high RPM. Some of those posting seem to be well-versed in anodizing beyond a hobbyist standpoint. I'm curious to know if this process would withstand erosive and corrosive effects at such pressures and flow rates. Should I just go ahead and send out the rails to be Type III anodized, or should I have a different set of rails made from stainless steel? The decision to make this engine flex-fuel capable came well after I'd had these rails fabricated so I'm stuck with them regardless. I can't seem to get a straight answer from the hot-rodding community. I have way too much invested in the rest of this engine to "try it and see" so if anyone here has experience and/or insight, I'd really appreciate it. Thanks!

Ken

1/9/2016 09:51:51 am

Hello Hugh,
Apologies for a late response but I wanted to check the ASTM and Mil specs before responding. I think that some readers will be reluctant to respond as it seems like a high risk concern for you and we really don't want to make a mistake. And I am not an authority but I have some thoughts for you to consider.First, 6L/min at 4 atmospheres is not really extreme. I think that the real issue is the possibility for corrosion. If the E85 was basic and it traveled through untreated aluminum it would be an attack mechanism. But, E 85 seems to have a pH of ~ 7.33, which is essentially neutral. But if anodized, the effect is a conversion coating that is a permanent as Al2O3 or sapphire with a mohs hardness of 9. So, I really do not see a problem by using anodized rails. I would have less faith in SS however. I would suggest further research at some of the metal finishing or metallurgy sites to check some more information. Having said all of that, the choice to proceed is yours and I offer only an opinion and not credible advice. It may be that there is no real answer other than perhaps a test rig to evaluate the process. Good luck in your search for the information, Ken.

Hugh

2/27/2016 07:42:58 pm

Thanks for the insight, Ken. I realized after I posted that the conditions are actually only really extreme in terms of automotive fuel systems, as opposed to transfer mechanisms, etc. My worry was the combination of those conditions combined with the possibility of corrosion. A snowball effect, if you will. I'm not looking to point fingers in case of failure, that's for sure. The project has so many other potential points of failure prior to rail corrosion becoming a concern that I may not even make it that far. Some of what I've read says water is a far greater threat to a fuel system than E85, but I'm not expecting water and haven't delved into the comparison. I've found a similar process to this for nickel-plating steel that I'm using for my fuel tank hardware, so I should have the better part of a reconfigurable rig left over from that.
I guess my next step is to anodize a piece of material and bath-test it. My hope is to dyno the car this summer, so I've still got some time to do it the old-fashioned way.
Thanks again for posting the article and also for your response!
Hugh

Guillermo

2/8/2016 01:05:42 pm

Hi, I've been trying to do this process, don't know if this post is still active. When I made the circuit it began everything ok, I waited for 1 hour while bubbles where very energics. I was using H2SO4 and an aluminium anode and aluminium cathode. When i got the piece to get color on it, it was brighter than before and it had less sice. What can be the problem there? thanks

Ken

2/8/2016 03:57:47 pm

Guillermo,
So, you are using sulfuric acid and not the sodium bisulfate in my process? That's fine but I have no idea what "less.sice" is.Please explain and maybe I can assist. Thanks, Ken.

Rod

2/8/2016 05:58:38 pm

I suspect they mean LESS SIZE and it coould be they had the Polarity reversed.

Ken

2/9/2016 10:19:08 am

Rod,
Good guess and quite possibly the right one. But, if the dimensional stability was so noticeable it seems that the solution to the problem would also be obvious. Good point about the reversed polarity. Thanks for the assist, Ken.

Leigh O

2/13/2016 03:51:56 pm

I am experimenting with aluminum sheeting for making jewelry and want to anodize from home. I'm interested in your process because it is perfect for small pieces and I live on the road in my RV with very little space.

About the cathode: I read that the cathode should be the same exact type of aluminum as what is being anodized. Is this true? I'm looking at anodizing a piece that is about 3x4 inches. Can I just cut a piece that same size and use that? Also, can the designated cathode piece be reused indefinitely?
Will a 6 volt rechargeable battery suffice for this project? I'm looking at using 24oz cups or glass jars.
When sealing the dye (I plan to buy from Caswell) is it specifically the heat that seals it or the moisture, or a combination. I met someone at a craft show who said she uses flame to seal the dye. (butane or propane). Does that work? The book on making jewelry from anodized aluminum that I have says she uses a vegetable steamer for 30-45 minutes which minimizes any runoff of color. Will this seal as well as boiling in water?

Okay, I think that is the entire barrage of questions that I have. I've been reading and researching for a few weeks and keep ending up right back here on your site. Thanks so much for creating this process for the chemically challenged!

Ken

2/14/2016 08:56:00 am

Hi Leigh,
The cathode can be any aluminum or even lead but aluminum is safer. It will release hydrogen bubbles during anodizing and the anode will release oxygen. But, it can be considered a consumable but it is a slow process and be sure to clean the cathode periodically and remove it from the electrolyte between uses.The cathode should be at least as large as the anode. 6 volts will work but it is more about the current and the anodizing is time related. Lower current will take longer but experiment to determine effectiveness. If the pores are formed sufficiently, the dye will penetrate and sealing is best accomplished by immersion is boiling water. If the anodizing is done correctly, the dye will seal quickly and not be removed by the hot water. But, you could also consider nickle acetate. But the boiling water is fine. Hope that these answers help and reading the link to the encyclopedia of electrochemistry might assist you as well. Best of luck, Ken.

Leigh O.

2/14/2016 05:34:29 pm

Thanks so much Ken. You're the best!

Spencer Brown

2/24/2016 06:10:23 pm

Do you leave it hooked up to the battery when putting in the dye.

Ken

2/25/2016 09:04:42 am

Hi Spencer,
The dye is NOT put into the electrolyte ever. After the anodizing is complete the piece is placed in the dye in a separate container with no current. Ken.

Jaxom

3/8/2016 02:32:20 pm

I was trying to anodize aluminum chainmail, because it's the same element, right? Despite following the process to the best of my knowledge, only the ends of the woven cylinder (Full Persian) were colored following the boiling process.
While I'll be trying a couple more times, if I'm making an 'obvious' mistake I would be grateful to hear it.

Ken

3/8/2016 03:40:11 pm

Hi Jaxom,
There are at least two issues with aluminum chainmail over the steel that would concern me. The first is continuity. The fact that links can be electrically disconnected would stop the anodizing. This would be particularly troubling if the chain had a good oxidized layer and was essentially a non-conductor. Aluminum chainmail is well known to have problems with links falling off as well. The second problem is that of the alloy used. Some alloys just do not accept anodizing and I have no idea what this alloy is and if it is a difficult one to anodize. The etching step may be not working to clean the oxide layer as well. This will be a real challenge to anodize and dye. I can't explain the cuffs at this point. Best of luck, Ken.

Rod

3/8/2016 03:40:12 pm

I doubt this will work. for you.

The problem is that as the andozing layer grows on the surface the aluminium ceases to be conductive.

The coating will not conduct the current required to run the process. As Chain Mail is made of individual links as the process starts each link becomes insulated from the next and prevents the reaction from taking place.

Unless you can find some fine Titanium Wire that you can weave thru each and every link to insure there is a contact spot it's not going to happen for you

Jaxom

3/8/2016 04:25:51 pm

So despite anodizing chainmail being a bad idea from the start, I'm gathering I'd likely have the best results if I hung them from a titanium loop in the current step. (assuming: bright aluminum is anodizable because it worked on some of the links; the lye step works as intended; I have them as individual links and not a weave to increase chances of contact)
Thanks for the advice, I'll be back once I have some better data. Of course I'll run the experiment with aluminum rods/bars to be sure I've got the process correct, but that's what I get for doing science before I took CHEM1411. >_<

Carl

3/13/2016 11:11:17 am

some of the sites state to desmut after the caustic bath. when I did the caustic etch the part came out a dark grey.
From what I have read that coating needs to be removed before anodizing, as it is the copper in the aluminum on the surface.
You make no mention of that. Are there some alloys that do not produce that condition?
Thank you

Ken

3/14/2016 11:17:18 am

Carl,
The etching step is optional and the grey color may be that the NaOH solution was too concentrated or it was in the solution for too long.There are some interfering alloys as covered in several of the comments,. But the overall procedure is the same as it would be with battery acid only safer. For most anodizing I have never had to desmut. Hope that this helps, Ken.

Mike

4/9/2016 08:29:51 pm

Hi I live in a place where its hard to get the pool chemical you described I have access to old car batteries. Once the batteries are discharged, is the material inside still sulfuric acid, and OK to use for anodizing? I can get the lead post, or just use a large fish sinker and flatten it out. Im trying to anodize some aluminum reel spools. Are there alternative sources for getting the chems you describe for the pool solutions? Also, why is lead used for the cathode? Can aluminum be used as well. I have access to Drano, is that good enough for the etching?

Thanks and regards

Ken

4/10/2016 09:28:57 am

Mike,
The liquid in batteries does contain sulfuric acid but the concentration is variable and depends on the specific gravity. So, it can be used but some experimentation may be necessary for best results. You do not need lead as aluminum can be used as the cathode. The chemical used is sodium bisulfate and has no substitute. Drano is sodium hydroxide and is used for etching at 2 %. It might be helpful for you to watch the video or read the write up again as this process is pretty clear. Best of luck, Ken.

Rich

4/11/2016 07:34:59 am

Just tried this method over the weekend. Great results!
Thanks for the wealth of information.
Rich

Nick Froome link

5/4/2016 10:29:33 am

I would like to anodize aluminium front panels with multiple colours. Has anyone tried painting dyes directly onto the panel and using more than one colour at the same time?

I understand that, if this process is possible, the dyes will tend to intermix & spoil each other. That's part of what I am looking forward to…

Thanks

Jacob link

5/4/2016 06:07:33 pm

I'm having an issue with the process. Whenever I try to anodize a piece it does not work, unless my aligator clip for my + wire is directly attached to the piece. If I attach the clip to an aluminum wire/foil that is touching my piece, the piece turns whitish (like the cathode usually does) and does not get anodized.

Ken

5/5/2016 10:03:44 am

Hey Jacob,
I can appreciate your frustration with the need for a good connection for effective anodizing and we all face the same problem. There has to be continuity between the piece and the power supply sufficient to provide the necessary current for anodizing. There is no way around this in any anodizing system. Also, as anodizing proceeds, the conductivity of the piece decreases. You can use aluminum alligator clips and just move them around the piece for uniformity. Drill and tap holes in areas that won't show, use homemade aluminum springs or whatever you need to make the connection secure. Sorry, no easy answer. Ken.

Chanan

5/9/2016 02:35:18 pm

I have a Voltec HY 3020EX power supply with over voltage control knob. I was wondering, if I should adjust that all the way to the right while anodizing. I guess I should also move the voltage knob all the way to the right and set the current to the correct setting determined by the parts surface area.

On a side note, lets say that the parts develop a yellowish tint after being in the bath the prescribed amount of time. If I were to remove the parts for inspection before completion and then while dying, the dye would seem to take up, but upon boiling for sealing all the dye would leach out? Would everything run amok like that because I removed and replaced the parts in the anodizing bath prematurely. Everything does check out while continuity testing, but the dye just doesn't take.

Ken

5/10/2016 10:13:45 am

Hi Chanan,
The current is more critical than the voltage so watch that setting as anodizing is progressing. If the dye does not take the part is either not anodized but has the yellow tint, or the part has been anodized but the holes have been sealed while anodizing. This could happen if the temperature of the solution gets too hot, or the part is simply not anodized. Check for continuity on the part and if it is an insulator it is anodized but the holes are sealed. Ken.

Chanan

5/9/2016 02:37:54 pm

forgot to mention, since I am already etching the part with NaOH, is there a problem if I prep the part with a light blast in aluminum oxide?

Ken

5/10/2016 10:16:41 am

Chanan,
No problem, but clean the part with either detergent or solvent before putting in the solution. Ken.

Chanan

5/20/2016 02:59:08 pm

finally had success. Now I need to improve my racking. so far I am using titanium wire. I have been able to source some pretty cheap titanium wire or titanium welding rod online. does it make a difference if I use either? If I was to acquire Ti rod that is .08" diameter will that be springy enough so that I can sharpen the ends and keep it say .01-.005" longer than any part pockets and clamp in the pockets? anybody got any rule of thumb or something for length of clamp and how much to make it longer than pocket depending on part pocket length? What If I had a 1" long pocket or say a .2" long pocket? I wanna get a good hold for all the cleaning dipping, anodizing, dying and sealing. Thanks everyone

Jayson

5/22/2016 09:01:39 am

Hello Ken. I wanted to thank you for the video and information. I am legally blind and disabled, but attempting to build an AR-15 simply to prove to myslerf I can and not feel completely useless. The firearm will be more of a work of art than anything.

I had an error in cutom painting the lower receiver that is anodized 7075 aluminum and was told you use permatex paint stripper as it did not have toxic chemicals and would not destroy the anodizing, but it did eat the anodized barrier as well. I like this process as I do not have to use battery acid and I have acquired everything I need to re-anodize my lower receiver. The only question I have at this time, is if there is a certain material the container the anodizing takes place in needs to be made of?

I have Caswell Olive Drab dye, distilled water, sodium bisulfate, aluminum cathode, and nickel acetate for use with boiling seal process. I will also use a battery charger for the power, but not sure what material to do the process in for the best results on a precision piece?

Ken

5/22/2016 03:54:54 pm

Hi Jayson,
I have never used a paint stripper on an anodized surface and was surprised that it removed the existing dye. That is a good heads-up for all of us. As far as the container used for the anodizing the best would be a good plastic or glass container. As long as it is an insulator and resists an acidic environment you will be fine. But remember not to let the mix get too hot as the anodizing is not as good. Glad to see your determination and I think the only really disabled are the ones who don't try. Best of luck, Ken.

JAYSON link

5/26/2016 10:24:34 am

Ken,
I wanted to pass this information along to you and your readers that may do art work with paint on or around their anodizing. As mentioned, I had an incident and ended up with paint all over my anodized item. It was drying faster than I could get it cleaned up as there was so much paint, so I used paint stripper to clean it up. The problem was it removed the anodized coating as well. The active ingredient is usually a chemical called methylene chloride and that is what removed my anodized layer as it is very harsh.

Another anodized piece was also messed up in the incident, but seeing the stripper removed the anodized layer on the first piece, I did not use it on the other piece so the paint dried as I was cleaning up the disaster. I tried Permatex brand Paint Stripper on it as I used it to get paint off of some plastics. I had seen youtube videos it would not destroy plastics like paint strippers, oven cleaners, and the other methods people use to remove paint. So I tried it on the anodized part as well. You spray it on, let it set 10 minutes, and then rinse off with water. The paint comes off with the water, but the anodized surface remains unharmed. You will want to wear nitrite gloves when doing this as it can still cause chemicals irritations, but it is not as harmful to you or the anodized items as the common paint strippers.

http://ecx.images-amazon.com/images/I/51q0syYPbvL._SX466_.jpg

Ken

5/27/2016 05:03:52 pm

Jayson,
Thanks for the information and I didn't realize that methylene chloride would remove an anodized surface. Here, it is sold as "Zip Strip". More good knowledge to add to our community. Thanks again,Ken.

Jayson link

6/8/2016 08:40:05 pm

Ken, I love science and mathematics. So thanks for the info as it gave me a good starting point for my project. I am aware most of your testing is on a small level more for craft items. I am building an AR-15 that will function, but in all honesty will be more a work of art with a themed design.

Using my science and math background I expanded on this to hard anodize the lower receiver that had the anodized layer damaged due to paint stripper. I had professional dye from Caswell and was going to use it, but decided against it as it fit my design better without the coloring and the aluminum under the damaged anodized layer was flawless.

I am going to document my whole journey and customizing via youtube, and after explaining the incident that damaged the anodized coating address completely removing it and re-finishing it. I will credit you and link back to this page as well as your updated youtube video.

I used a 25% solution on an item that was in 16 cups of distilled water plus the sodium bisulfate for the anodizing bath. I lined a plastic container with Aluminum flashing and had extra bend over the top in the corner to form a tab to connect my negative charge to. For a power source I used a 12v 6 amp manual battery charger. The item was thick 7075 Aluminum and anodized in the bath somewhere between 45 and 60 minutes.

It looks great and I am so happy with it. I even think it looks better than it did before with the anodized layer it came with from the manufacturer.

Ken

6/9/2016 03:38:06 pm

Hey Jayson,
Thanks for the update and information and we look forward to more input as you follow your project. Continued good luck! Ken.

arnel tolentino

7/6/2016 07:44:28 pm

Hi Ken, I plan on anodizing some aluminum parts, its size is about 7inch long, 3/4 in width and half inch thick for the most part.
I want to know first if my plans are in right direction.
All materials to be mentioned are the only ones that are available in our area.
1.Clean with purified water(no distilled water available in our area)
2. Degrease using mixtures of purified water and dish washing liquid (with degrease formula). Bath in warm and bubbling container for about 10mins. Then rinse.
3. Anodize. I will use lead wire(used for soldering) as cathode, and lead wire also to hold the part I want to anodize as well.(pls comment if this is ok to do)
Mixture will be 50% battery acid 50% purified water. Using 12v battery charger of our car. Yes car battery charger! Dip it for an hour.
4.rinse it in purified water.
5.boil in hot water for about 20minutes. (Yes I will not dye it)

Pls comment if this are ok to you. And see it fit for the project.

Ken

7/7/2016 03:45:36 pm

Arnel Tolentino,
Everything sounds good except the cathode. Remember, the cathode must be at least as large as the piece to be anodized. That is a lot of lead solder. Perhaps consider a scrap piece of aluminum. Best of luck, Ken

arnel tolentino

7/7/2016 04:52:24 pm

Ken, unfortunately I cant find anypiece of scrap aluminum af home, the only Idea I have is an aluminum foil.
Can you suggest anything that is aluminum that can be easily found at home? Maybe Im just overlooking thing here.

Ken

7/8/2016 09:12:09 am

Arnel Tolentino,
The only thing that I can think of offhand is old aluminum cookware. The foil may work and I guess if that is all that you have it is worth a try. Ken.

mike

7/12/2016 08:09:21 am

Hi Ken,
I anodised a piece of aluminium yesterday using foil as a cathode.
surface area of object 48sq inches. today I slightly diluted the solution, bisulphate to cover the object in a vertical position. The current was in both cases about 8A initially which dropped to 5A. To my horror after an hour and a half I found the piece to be pitted and eroded really badly. I coloured it anyway by way of a test.
The thickness of the piece is 2.5mm and has been eaten through completely in several places. The pits are about 5mm in diameter.
When I now look at the first piece i note that there were 2 pitts in one side too. One side of the badly eroded piece is worse than the other, the piece was in the middle of the bath. Ambient temp same as yesterday around 30C.
Cheers
Mike

Ken

7/12/2016 09:35:16 am

Hi Mike,
Unfortunately I was not completely clear about your result. Are you suggesting that the use of aluminum foil caused the pitting in the anodized piece? If so, did you pre-clean the foil? I have tried to find out what most foil is alloyed with and it appears that it is frequently made from recycled aluminum. Thanks for the comment as this may be very helpful to others who only have foil available. Ken.

Hanan

7/12/2016 10:25:52 am

Did you weigh the NaBisulfate or go by volume? How accurate a scale did you use? I'm thinking that your concentration is so strong that after the anodize layer is created it just starts to corrode more metal than Oxide buildup is occurring.

Ken

7/12/2016 03:33:50 pm

Hanan,
As indicated in the write up the 20% is by weight and the scale that I use is a pocket variety with no special sensitivity. A small variation in weight is fine and will not cause a problem. This is not a strong solution as the sodium bisulfate is a half salt of sulfuric acid. Any solution including the battery acid variety has a pH of 1 or 2 and will corrode most metals. But, during the anodizing the aluminum is building an insulating layer and will not corrode the Aluminum. Ken

mike

7/12/2016 11:57:59 pm

I used foil off the same roll. In the first instance I used a tray with the foil underneath and 2 layers of plastic mosquito netting with the piece horizontal on top of this netting. I had to constantly force the netting down because of the gas buidup underneath the netting. the 2 pits that were made were on top strangely enough.
The second piece was done in a bucket with the same foil area but with the foil running down the sides and across the bottom. Mosquito netting was then placed inside and a large piece of teflon was placed on the bottom. The piece was hung in the middle.
the big difference was that I diluted the solution from the day before by about 3 to 1 with tap water. This means that the diluted solution would appear to be the cause of the problem, hardly the metal being eaten away by the acid which is now much weaker.
On a side note I also repeated a small piece 8sqins at 0.5A as the previous day in the same small bath, same original solution, same time 1hour. results were completely different. the only thing that changed was the PSU, the first time 15V limited to 1A and this second time a 13.8V 9A supply, current was the same both times at 0.5A monitored with an AVO on 10A scale. Maybe there is an effect caused by the AC component in the supply?
If you pm me I will you a picture of the pitted and corroded piece.
Cheers
Mike

Ken

7/13/2016 03:59:54 pm

Hey Mike,
There are several thoughts about these problems that concerns me and coming to a possible solution. The first is that there are too many variables to narrow down a cause. The second is that the anode is so thin (2.5 mm) that in trying to make the surface pores the excessive current has no choice but to eat away the material. The third is that in thee dilution scenario, it sounds as if you are simply performing electrolysis of the water using the sodium bisulfate as an electrolyte. Perhaps it would be worthwhile to try a small piece with greater thickness of known aluminum with the foil as the cathode to test the standard solution. This system has good repeat ability with no problems as you have encountered. It may be that very thin stock just cannot be used. Let us know what you think. Ken.

Ted Mitchell

8/23/2016 01:38:44 pm

I make a product using 6061 aluminum which I normally finish with either a brushed (sanded), bead blasted (with a clear coat) or powder coated black. I am going to experiment with clear anodizing, and black to see how they come out. I just doing an experiment with a scrap piece with part of it bead blasted, and using a battery charger to power it. It started to bubble violently on 12v 2amp, so I lowered to 6v 10amp, but after a few minutes I raised it back to 12v 2amp and it is showing only about 2amps on the meter (very poor accuracy). I looked at the scrap piece after about 5 minutes and it is showing a radical change in appearance already, but I am going to let it percolate for about an hour and then try to seal it in boiling water. I used distilled water and HTH down to make my solution and aluminum foil for the cathode.

Ted Mitchell

8/23/2016 01:44:23 pm

I forgot to mention that I used a battery acid tester to check the acid and it was just above 1225.

Chanan

8/23/2016 02:38:56 pm

If you pulled out the part any time during the anodizing bath, the dye won't take. I suspect that when you pull it out the cell structure does not grow sufficiently and then it doesn't soak up any dye as the cell structure is too far under .001" .

Ted Mitchell

8/23/2016 04:59:59 pm

I was trying this time to just clear coat the part. The dye test will come later. I am disappointed that the result was mottled, but on looking at it carefully, I think that I rushed the bead blasting, and that wasn't even. Tomorrow I am going to try a new test and clean the part before blasting and then doing a better job at that stage and see if I can get a more consistent result. If that works out well, then I will try the dye.

Ted

8/24/2016 04:25:43 pm

Well, unfortunately, I am still getting a mottled appearance. It looks like part of the finish is not dry. Some parts are darker than others. I don't know what I am doing wrong. Maybe it is the aluminum foil as a cathode.

Ken

8/24/2016 05:29:36 pm

Hi Ted,
I have been following this thread from your first post and my initial thought was that the aluminum foil was a strong possibility. When I first developed this process I avoided foil as it is frequently alloyed with many unknowns and is typically made from recycled aluminum. I think that it would be worth picking up some 6061 from the hardware store or even lead flashing from the Home Depot or other source. Just as long as it is at least equal to or greater than the piece to be anodized. How about just try a small piece to at least eliminate that possibility? Please keep us updated. Thanks, Ken.

ted

8/25/2016 01:32:09 pm

OK, I used a piece of 6061 scrap aluminum for the cathode, and still get a non-uniform color. On my present parts, I am bead blasting and then clear coating with nyalic and have no problem with a nice consistent color, but I thought anodizing would give me a better permanent protection if I can just lick this problem.

Ken

8/26/2016 09:53:48 am

Ted,
If the problem is not the cathode material, the post-bead blasting cleaning is good, and there is no index of refraction concerns, I am at a loss for additional ideas. I am making an assumption that you have anodized a non-bead blasted sample and it was acceptable. Time for a coffee break while I think. Ken.

Ted

8/26/2016 11:54:18 am

Yes, I did a brushed aluminum (sanded) piece and it looked good, but I really couldn't tell that it was anodized since I didn't dye it. I am trying a new bead blasted piece now. I only clean the piece after blasting with acetone, but the finish before anodizing looks perfect. I am waiting for my Dylon dye to come in the mail.

Ted

8/26/2016 02:27:15 pm

NO, my latest bead blasted today came out with light and dark areas again. Before anodizing it looked perfect and even.

Hugh

8/26/2016 04:30:07 pm

I think your problem is with the bead-blasting process itself. It's gentler than sandblasting, but you're still essentially shot-peening the surface to some extent. It looks even when coming out of the blaster, but it's not.
A couple of suggestions:
Rather than acetone, wash the parts in a warm, soapy solution. Pretend you're doing dishes like stubborn pans. Use a plastic or stiff horsehair bristle brush--nothing metallic! Rinse well with warm water. Once they're dry, try the process again. Any small pieces of bead or free aluminum will be lifted from the surface pores of the material by the warm water. The soap is important because the lower surface tension allows the water to get deeper into the pores, and makes it harder for the tiny particles to do anything but be rinsed away.
If that process alone isn't enough, after blasting go over the entire surface--every nook and cranny--with a brown Scotch-Brite pad (the ones at auto-parts stores). Follow that with the entire warm, soapy water/rinse procedure and try again.
I think you're encountering microscopic surface contamination during the bead-blasting process. Chemicals like acetone and even brake cleaner actually drive the contaminants further into the metal's surface due to their higher surface tension and fast rates of evaporation.
We get so enamored of chemicals that we forget the Universal Solvent. A little soapy water and some elbow grease go a long way!

Ted

8/27/2016 08:49:05 am

Actually, one of my samples did include using soap and water after the bead blasting. It was one where I blasted one side of the sample and the other side with sanding (brushed look). That was the only one that was not bead blasted. I am wondering if the fact that I am using an aluminum cathode, which transfers some aluminum to the part on top of the blasted surface during anodizing by electrolysis.

Ted

8/27/2016 09:00:35 am

BTW, how do I attach a picture.

Ted

8/28/2016 03:35:59 pm

I just tried 2 more pieces which I carefully cleaned with acetone before blasting one side only, the other side sanded, and then scrubbed with soap and water after. One sample was then etched in Sodium Hydroxide, and then anodized. The blasted samples where better but not good enough to use on my part, both sanded samples came out good. Still waiting on my black die. I am hoping to get as good results as Adam G. and Jeremy to replace my powder coated part. I wonder how to get a good dull finish without bead blasting, or maybe the bead blasting would turn out ok with the black dye.

Ted

8/28/2016 05:47:41 pm

http://i346.photobucket.com/albums/p433/ted125/006_zpsoatsjsfm.jpg

Ted

8/31/2016 02:20:48 pm

I recently read on finishing.com that one way to even out bead blasting was to anodize, then to strip the part and then to re-anodize again. Has anybody tried this?

Ted

9/3/2016 02:30:37 pm

Ok, Ken.
I tried stripping a couple of bead blasted parts, and then re-anodized them. They did come out without the mottling, but then wouldn't take any dye, so I don't know if they are anodized or not.

http://i346.photobucket.com/albums/p433/ted125/002_zpsvbswoqyb.jpg

Ken

9/4/2016 09:21:01 am

Hey Ted,
After looking at the photos the problem is that I can't see whether or not there is a yellow tinge which is typical of anodizing. Clearly there is a problem with formation of the cell structure and depth but I honestly can not say what is happening. I have no history with bead blasting so have as many questions as you do. Sorry for such a limited amount of input but I am trying to be as honest as possible. Ken.

Ted

9/4/2016 03:21:41 pm

I really don't think they re-anodized. There was no yellow tinge, but there wasn't any on the first time thru either, Also after the parts dried, they weren't as perfect as I thought, they had sections of the surface that kind of looked like sand or dirt. I am about to give up on this whole idea, especially as I can't dye them either.

Mark

9/9/2016 06:33:03 am

Hi Ken,

this may be a stupid question but I was thinking, why can't a person use a diluted solution of black acrylic paint in place of black dye? or say something like a really thinned out mixture of lacquer based Duco as opposed to using clothing dye? .............. I see no mention of this anywhere. The only thing that I can think of that may be prohibitive is the molecular size of the paint molecules, strangely though I have seen mention of using toner from a laser printer!

Ken

9/9/2016 09:42:38 am

Hey Mark,
Not a stupid question at all but the fact is that the dye (color) has to be in solution to effectively color the micropores. Most paints are in suspension and the particles are far to large to be useful. The same would apply to toner as the particles are even larger than those in paint. It may be possible to surface coat metal with toner but it won't dye the pores. Thanks for the comment, Ken.

Mark

9/11/2016 03:35:31 am

Hi Ken,

thanks for the reply. I've seen complaints about balck clothing dye not producing a rich black but rather a bronze type colour. is there a way around this? I'm thinking if one was to take a powder type dye and rather than follow suggested mix ratios on the packaging for clothing rather saturate the mix for the quantity of water needed. The other thing that got me thinking is the dye in the part must get diluted a little too when you boil it in water for sealing. What about keeping to two mixes of dye, one at room temperature for dyeing the part and the other for boiling and sealing, would this make a difference? or is it too much effort for too little difference?

Ken

9/11/2016 08:42:26 am

Hey Mark,
The concern and problem with black clothing dye is that is never going to be black on a metallic surface.The chemistry is just too unsuitable so your last statement is mostly true. The effort is just not justified. Thanks, Ken.

Riley

9/20/2016 07:19:58 am

Hi Ken,

I have some aluminum RC parts that have faded in color from a deep rich blue to almost white over the last 18 years. I've striped the parts with greased lightning and polished them with a 15,000 grit paste, but now they wont anodize. Have I prevented the parts form anodizing by polishing?

Ken

9/20/2016 03:23:02 pm

Hi Riley,
If the solution is correct and the electrical connections are good, then something is causing an insulating layer on the aluminum. I would try cleaning extremely well and testing conductivity of the piece. I would also suggest a mild etch in NaOH. If that fails to work I am at a loss for other explanations. Ken.

jan beck link

9/28/2016 05:21:09 pm

I did some experiments, and it turns out that you can use sodium bisulfate for hard anodizing as well....

https://sites.google.com/site/janbeck/safer-hard-anodizing-of-aluminum

just thought that might help somebody out...

Ken

9/29/2016 10:38:01 am

Hi Jan,
5 years ago when I first experimented with sodium bisulfate I attempted to accomplish hard anodizing with mixed results. The process controls are much more rigorous and more difficult to quantify. I was using the ASTM standards of abrasion and electrical insulation tests as the metric for thicker and more durable surfaces. I think that the scratch method is too much of a subjective measure and really difficult to use as a definite criterion. I still think that it is possible to hard anodize with this method but I was not able to convince myself that I had succeeded. But, your results are interesting and well worth a try. Thanks for the post, Ken.

Mark

9/30/2016 06:26:41 am

Hi Ken,

Any chance one can use stainless steel bolts and nuts for making decent connections to the part to be anodized?

Ken

9/30/2016 03:25:29 pm

Mark,
There are several problems with using SS as the contacts: The first is that sodium bisulfate is the half-salt of sulfuric acid made from sulfuric acid and sodium hydroxide.and behaves like sulfuric acid. The SS may last a little longer but depending on the composition, may decay quickly. The fact that SS is dissimilar may lead to an electrolytic decomposition of the electrolyte. If I wanted to use threaded material I would go with aluminum machine screws. The ASTM standards do list SS as suitable for transporting H2SO4 but not in an electrolytic environment. That is at least my 2 cents and others may disagree. Thanks for the comment, Ken.

Mark

9/30/2016 11:18:01 pm

Thanks Ken,

connectivity is a huge problem! I'm trying to anodize a huge heatsink for an audio amp I'm building. So after trying smaller jobs and having good results with Sulphuric acid, I tried to anodize this large piece of square tubing for the amp. I calculated it would require 10+ amps. So I had two battery chargers in series, froze two 2 liter bottles of water, I put my acid tank in a larger tank of water and added the ice bottles. Ran it for an hour +, almost cooked one of my battery chargers and vaporized my conductor. only to find it didn't work. I'm pretty sure my conductor got anodized before my part did. So I'll need a better way to secure my conductor to my part ( I thought of using pop rivets since these seem to be aluminium, going to have to search this side of the world for Aluminium bolts and nuts! ). I've now bought some Sodium Bisulphate. I'm going to try that soon too

Addi G

11/7/2016 12:22:36 pm

Hi Ken, I was wondering if you had seen any noticeable differences (esp. over time) between pieces that had been anodized using sulfuric acid vs. sodium bisulfate

Ken

11/7/2016 03:10:09 pm

Hi Addi,
Since the sodium bisulfate is a half-salt of sulfuric acid there should be no difference and I have found that to be true with one caveat. I have done abrasion tests and found no discernible changes. However, the one area that may make a difference is in the dye color with UV light. But, this would be true with both systems. Once the dye is sealed in the RIT dye may be more light sensitive but I have not confirmed that to be true and it is my best guess. But, generally speaking both processes are equal. Thanks, Ken.

Ben

11/9/2016 09:24:28 pm

Ken,
Thanks a lot of all of the time you put into this anodizing write up, videos and answering questions. Also congratulations on the success you have had sharing your information. I have some questions about your process. First, Is there a reason that you recommend 20-30 % sodium bisulfate? Is that where your best results happened or is there a different scientific explanation for that? In what circumstance would you bump it up to 30%? Also do you think that sodium bislufate as an electrolyte can produce the same results as commonly used acids? Thanks for your help and sorry if you have already answered these questions in previous comments.
-Ben

Ken

11/10/2016 03:24:32 pm

Hello Ben,
The amount of sodium bisulfate used was determined by both an empirical and experimental approach. Since the bisulfate is a half-salt of H2SO4 it is easy to calculate the amount needed. The higher amount is needed when higher current and longer anodizing times are used as the electrolyte is depleted. Of course, the evaporation of the water slows the degradation but the range suggested works equally well for most processing.And, sodium bisulfate is as effective an electrolyte as most acids. Thanks for the kind words and questions, Ken.

ben

11/10/2016 04:49:45 pm

I like that ken, Thanks!
Ben

Daniel

1/5/2017 09:27:05 pm

Hi Ken,

OK, so I've run into a problem. This is my setup:

First, as you said, I put my aluminum piece in a lye bath at first. Then I rinsed it in water.
For the anodizing bath, I've created a a 20% solution of sodium bisulfate with distilled water. I attached my anode, a small piece of previously etched aluminum, to the positive end and the cathode, some aluminum shingles from Lowes, to the negative end. My power supply is a rechargeable battery that delivers 12 volts at 5 amps.
After setting this up I let it run for about an hour. I took out the piece, rinsed it and put it in the dye bath. After 20 minutes in the bath, I noticed the piece had barely taken the dye AT ALL!

What do you think I'm doing wrong? Am I not cleaning thoroughly? Am I low on voltage/amperage?

Thank you.
Daniel

Ken

1/6/2017 03:28:54 pm

Hi Daniel,
Assuming that you do have a 20 % solution I would look at three possibilities. The first, and most likely is the electrical connections to both anode and cathode. They must be secure and complete. The second is the "aluminum shingle" from Lowe's. Is it really aluminum or some alloy? Both aluminum and lead are good cathode material. What is the dye and its concentration? Try raising the temperature of the dye solution if it is a good dye. Watch for bubbles at both the anode and cathode to test ionic transfer. Let me know what you find as this system will work! Thanks, Ken.

James

1/31/2017 08:45:13 am

Hi Ken,
First let me say how helpful this site has been the me and what an incredible help you are to us all...thank you.
A few basic Qs right off the bat....

1. Using ph down, what should my ph level be in my bath before starting the anodiztion process?

2. With a bath volume of 1/2 gallon distilled water and work peice made of unknown grade of aluminum the same volume of just under that of a half dollar....I have used a 12 volt power tool battery
Not sure about the amp out put...what are your thoughts?
I have other higher volt battery's 18,28 volt.

3. Anode n cathode are both aluminum from lowes a thickness of
1/8" wrapped in 18 gage aluminum wire running back the battery.
I have not prepped the anode or cathode with any type of sanding or etching....thoughts?

4. The work peice has been thoroughly sanded with sand paper
To a shinny brushed finish. Then a quick dip in lye for 5-10 seconds
A quick dip n shake in distilled water then on to the anode with good secure contact....thoughts?

5. Battery is conecthed anode to positive n cathode to negative.
Cathode begins to give of a steady strong consistent amount of bubbles. 30-45 minutes later the bubbling has refused by approx 25%
And the work piece has turned a dark sooty grey. A small amount of the grey sooty matter can be seen floating around the tank as well.
After taking the peice out, giving a rinse and wiping ...half or more of the soot/grey comes off but the peice is still noticbly darkend grey:(
Thoughts??

This is as far as I want to go at this time because I feel that attempting a dye bath, even if sucsessful would result in a poor dull finish.

HELP!!!!
Please.

Thank you for your time and attention,
James

Ken

1/31/2017 03:45:37 pm

James,
The pH will be 1 or 2. The voltage is fine for that size of work piece. But, I am confused by some of your comments.
3. Anode n cathode are both aluminum from lowes a thickness of
1/8" wrapped in 18 gauge aluminum wire running back the battery.
"I have not prepped the anode or cathode with any type of sanding or etching"....thoughts?

4. The "work piece has been thoroughly sanded with sand paper
To a shinny brushed finish". Then a quick dip in lye for 5-10 seconds
A quick dip n shake in distilled water then on to the anode with good secure contact....thoughts?
You say that you have not prepped either the anode or cathode but the work piece was sanded and that is the anode! So, I am confused. Do you have an anode in addition to the work piece?

James

1/31/2017 05:16:23 pm

Hello
Thank you for you fast response.

I should have been more clear, I'm still getting the proper
"Lingo" down:)

My aluminum work peice was securely "cradled" on
Another peice of flat aluminum that is the same type of
Flat aluminum used for the cathode.

I'm acutely leaving lowes as I type this because I wanted to start fresh
So I went out to purchase more flat aluminum and realized that it was
Advertised as pre anodized!!! So I looked for another peice that was not and did find one.

I'm still a little perplexed though because on another previous attempt I instead of using the flat cradle anode decided to securely wrap the work piece and had the same results. I never did change the cathode though.....

Thanks
J

James

2/1/2017 01:06:31 am

Hi Ken!
Quick update....
I finally had success!!
Tonight I used the new peice of flat
Pre anodized aluminum for anode and cathode but
This time sanded both with grit 60 sand paper.
Used my 12v power tool battery as power source
Let sit for 1 hour. After that I put in to red rit dye and after less then
15 min started seeing some results. After an hour I was home
Free with my first truly successful result that I was very pleased with.
Then trouble struck....
I replaced the flat aluminum anode with an aluminum belt buckle that
I want to anodize and let her rip. In less then 5 min I knew I was in trouble.
The work piece had turned a dark grey:(
Now I have been thinking about this and think that my problem
Might be in the alloy/grade of aluminum of the buckle of itself or....
In my sanding prep of it. I have been prepping the buckle with an
80 grit steel whoal type pad and think I'm deeply embedding
It in to the peice witch is then being oxidized by the acid. I noticed that after I disconnected the battery that the peice kept bubbling!
I'm going to start with a new buckle but this time only use the
Non metallic sand paper and see how it goes. I want to do it now
But it's 4am and I want to do this with a fresh mind.
Thanks for listening;)
Please let me know your thoughts at your earliest
Convince.
Thanks,
J

Ken

2/1/2017 09:12:20 am

Hi James,
Thanks for the update and you have hit the nail on the head. The way aluminum is alloyed is what causes the black sooty appearance. Particularly silicon, copper, and iron. And, decorative item are frequently from recycled aluminum and have questionable alloys. As far as sanding, I would avoid metal containing abrasives as they can be left behind to interfere with the anodizing. Regular hardware store 6061 is a good "control aluminum". Also, if you already have 18 gauge aluminum wire I would make a paperclip type connector and move it around every 20 minutes or so. Please keep us updated, Thanks, Ken.

James

2/1/2017 01:02:48 pm

Hello Ken
I'm really really hoping that it's not the buckle but, if it is....
Do you have any suggestions or am I SOL?
Another piece I'm looking to work on has some copper pins at hinge points, do you think that will cause issues ?
Thanks
J

Ken

2/1/2017 05:45:01 pm

James,
The copper pins should be OK unless there is heat involved. As far a the belt buckle goes if there is black soot as before you will be SOL. Let hope the next on is more aluminum than alloy. Ken.

James

2/1/2017 06:24:52 pm

About to go for it again.

James

2/2/2017 10:19:07 am

Hi Ken
So last night I had a successful attempt.
It wasn't what I was going for but it's going in the right direction.
I sanded the work piece up to a 1200 grit finish
With non metallic sand paper. Washed it with dish soap under
Tap water then rinsed in distilled. Connect directly to
Aluminum wire from positive. Put in the bath for 1hr 45min.
Then rinsed in distilled. The piece had lost at least half its shine
But I put it in the dye any way. After 15 min I could see it was taking .
It came out an hour later. It was dark and a little dull but it still looked pretty cool. Not bright red but a mahogany.
I'm glad to be headed in the right direction.
Any thoughts on why you think I might be losing the shine?

I have also noticed on other attempts that when
I have put a work piece in the bath halfway then after some time
The cathode stops bubbling almost completely
Then I submerge the whole piece and it begins to bubble.
What does this mean? Does it mean the surface area of the piece is anodized and will not anodize any further when the bubbles stop?
I know when a piece is anodized it is insulated and will not carry any current but what if a whole piece is anodized
Then you sand of the anodized layer of the front of it
Then sand off a layer some where on the back of it to connect the
Positive wire to? Will the sanded area then be able to "reanodize"?
Thanks again for your time.
J

Benny Profane

2/4/2017 03:50:11 pm

I plan on trying an anodizing project soon, but I still have a few questions. I gather that changes in voltage, current and temperature affect pore size, but there's no clear statement of the direction of change. I.E., does increasing current or voltage increase or decrease pore size?

I'm guessing lower temperature results in smaller pore size since hard anodizing is done at low temperature, but I'm not sure.

My goal is to produce a shiny black anodized finish on some bicycle parts. I'm assuming I'll need the Caswell dye with larger pores to acheive a high density, plus it will take some experimentation to get things dialed in. But some more information about the direction in which voltage and current changes affect pore size would be helpful.

Ken

2/4/2017 05:17:14 pm

Hi Benny,
Rather than repeating information regarding pore size and structure that is much more completely covered, please check the link at the end of my article write up. It sounds as if you really want to understand relationships and pore size and the electrochemical encyclopedia is the best learning tool that I have seen.Scroll down to "anodic oxide" and check the great information there. Thanks, Ken.
The link if you want to copy and paste:
http://knowledge.electrochem.org/encycl/art-a02-anodizing.htm

Powder Coating link

2/6/2017 04:35:35 pm

That was great information, very details and useful for a project I am working on related to powder coating aluminum.

Benny Profane

2/14/2017 11:20:43 am

Powder coating of aluminum works well. I had an aluminum bike frame powder coated and it turned out great. I don't know if you're planning on doing it yourself or having the job done professionally, but the key to good results is getting the aluminum CLEAN. Strip it of any old paint and thoroughly degrease the metal with acetone or isopropyl alcohol before powder coating.

If you are planning on powder coating something which has been anodized, I think removing the anodized finish will provide better bite for the powder coat.

Benny Profane

2/14/2017 11:12:27 am

Does anybody have any experience comparing the Caswell black dye with Dylon Ebony Black #8 dye? I'm looking for a dense black, and the Caswell dye costs quite a bit more than the Dylon. Rit black won't cut it. From what I've seen and heard, it produces a dark bronze color. Not a bad color, but not really black.

Kendall

2/19/2017 04:38:50 pm

Sorry for the long post but I need help.

So I've tried this process following the instructions and was able to anodize my first sample. However, I have since been unable to replicate it. (*) My overarching goal is to make stuff from melted aluminum/casting and I wanted to color it as well. However, my current goal of this project is to make a bunch of samples to test variables associated with finishes and colors.

I've spent most of the day trouble shooting and keeping notes so I can possibly isolate the problem. The problem is that I am unable to anodize.

The grade of aluminum I am using is 6245, flat bar I purchased from lowes which I've cut into squares and drilled a hole in to make a connection.

There were minor deviations between my process and the instructions provided.
-Doubled the Sodium Bisulfate so I could submerge my piece in a small mason jar.
-Used aluminium and steel wire for anode and cathode during several attempts due to tensile strength? and trouble shooting conductivity. I had to improvise for the first sample and used key rings as my anode/cathode contacts.

For Sample #1 I used a 6v 5 amp/h rechargeable battery. There was an immediate reaction at the cathode and tons of tiny bubbles. This step lasted about 30 minutes and I proceeded to the rinse, dye, and sealing process and was impressed with my piece and 1st time success.

When I go to repeat this process however, I hardly get a reaction at the anodize step, barely any bubbles. I've remixed all the solutions, re-cleaned and etched my samples, and checked the connections of my alligator clips that I hobbled together (no key rings this time), exchanged the 6v for a 12v 2.9 amp/h rechargeable battery, replaced the cathode.I used a multi-meter to test connections along contact points.

When I used the 12v battery I received the initial reaction that I had had before, lots of bubbles. However this only lasted about 15 or so minutes (the solution did warm up, thoughts on cooling it down?). I suspect that I am draining these batteries somehow but I can't figure out how. I also did not anticipate that this process would have that effect on the batteries. For the hell of it I've attempted to replicate the process but cannot seem to achieve the appropriate anodizing reaction. I am now waiting for a variable DC power supply to arrive next week so I can have better control over variables. In the meantime I am stumped while I literally and figuratively recharge my batteries.

(*) The melted aluminum I plan on using is from your typical soda/beer can that I've melted and made ingots from. Is there a way I can test the purity of this reclaimed metal? Also, am I wasting my time in thinking I'll be able to dye it?

I sincerely appreciate any help or information regarding the above.

Kendall

Ken

2/20/2017 05:12:42 pm

Hi Kendall,
I am glad that the process worked the first time and the procedure has been successfully used by many readers/viewers. However, the anodizing of cast objects can be difficult, to impossible,when using recycled material that cannot be determined easily.
The remainder of your post has way too many variables to isolate the problem and some seem like more than minor deviations. For example, doubling the sodium bisulfate approaches saturation and can cause problems. Changing power supplies and connections confuses the issue. Use aluminum wire and the original battery. The high current draw seems unusual so use the multi meter to determine what the current draw really is. There should be small hydrogen bubbles at the cathode but the solution should not get warm to hot. It has to be cool to warm. I was unable to find the aluminum alloy that you used in my charts so I am not sure if that is the problem. Sorry that I can't be of more help, Ken.

Kendall

3/20/2017 10:04:56 am

Thanks for the reply Ken, I've since received my variable power supply and repeated the process according to your instructions. I am thankful to say that I was able to anodize another piece! I think my problem rests with my aluminum (and steel) hangers. They appear to be dissolving for some reason and I can't figure out why. Any ideas?

Ken

3/21/2017 09:45:47 am

Kendall,
Steel will corrode quickly in the acid and my best guess is that it is a current draw problem. Try using heavier gauge wire and hangers. Ken.

Ryan

2/22/2017 05:32:27 pm

I have recently purchased some headphones with colored aluminum on them and I am wondering if I can use a laser cutter to remove the previously anodized layer of aluminum. Its also an issue that these aluminum parts have a bend to them and I do not know their precise dimensions.
Speaking of this, since it is already colored, could I possibly use a laser cutter over the whole aluminum piece, anodize it, color it, then repeat with another design in the center, so only the center is anodized, thus I will be left with a base color for the background of said design that has another color.

Ken

2/23/2017 09:33:39 am

Hi Ryan
I think that you are facing an uphill battle using a laser cutter as the anodizing color can be deeper that it appears depending on pore size. Coupled with the fact that there is not a lot of total aluminum and you have a bend or radius of unknown value make the possibility of success remote at best. That is simply mu opinion, Thanks, Ken.

Dave Ogden

2/24/2017 12:26:21 pm

re anodizing aluminum sailboat windows using your method I am getting pitting small holes any idea?

Ken

2/26/2017 04:26:23 pm

Hi Dave,
Unfortunately pitting is the most difficult problem to solve remotely. It depends on the alloy, how it was fabricated, contaminates from sanding, etching, and process control. If you Google anodized aluminum pitting you may get some clues but it is a tough nut to crack sometimes. Sorry that I can't be of more help. Ken.
PS. Also check to see if the pitting was there prior to anodizing.

Ryan

3/5/2017 07:06:22 am

What is the proper way to dispose of the different solutions once you have completed your anodizing or removing a previously anodized. Before I attempt this, I want to make sure I have everything in place I need. Thank you for your time.

Ken

3/5/2017 08:52:58 am

Hey Ryan,
The easiest way is to add the sodium hydroxide to the sodium bisulfate solution and it will produce sodium sulfate which can be put in the drain: NaHSO4 + NaOH → Na2SO4 + H2O. Or, you could also neutralize the acid with baking soda. There will be some CO2 bubbles but also can be disposed via the drain. Ken.

Ryan

3/5/2017 12:37:49 pm

Thank you so much. I assumed that was the answer, I guess I was just overcomplicating things.

StainlessSteve

3/27/2017 12:38:25 am

I think the alternative suggestion to NOT use sulfuric acid is what compelled me to continue reading your article. More attention should be given to the use of PPE whenever working with some of these chemicals is an absolute and not a suggestion. I have used the sulfuric acid method and find the risks out weight the necessity of home anodizing. I will try your suggestion to use the sodium bisulfate. One suggestion I have for readers is avoid the acrylic coating and use lacquer. I have used Rudd On-Site lacquer on aluminum automotive parts in the past and find that it holds up very well to weather and remains on the surface far better than clear acrylic coatings. When coloring remember reds and blue dyes fade more easily than other colors. And also hydrogen gas is very explosive, remember the Hindenberg! Only do your anodizing in a well ventilated area away from other metals you do not want to corrode. Great article, thank you for posting this...

Armand

3/31/2017 08:11:38 pm

Hey Ken, Wow lots of responses since I was here last.

I have a slight problem that you may or may not be able to help me with. It seems that when ever I anodize any aluminum that is knurled some (if not all) of it wants to turn patchy black in the knurled areas. I have tried scrubbing it to death and even etching it for quite a while before anodizing but my result is always the same. I always use 6061 aluminum and the results are very unpredictable. As a result of this problem, I either etch the anodized knurled parts to remove the blackness that sometimes shows up or I just don't anodize those parts at all. So I was just wondering if you or any of your followers could shed any light on this problem?

Ken

4/1/2017 03:31:48 pm

Hi Armand,
There is a similar problem with black anodized knurled aluminum and it has to do with the fact that the oxide grows perpendicular to the metal and the sharp edges of the knurl cause irregular growth and dark colors. I would try buffing with a felt pad to break the sharp edges and clean thoroughly and try it again. I may have gone down a rabbit hole here but it is my best thought so far. Please keep us informed, Thanks, Ken.

Armand

4/4/2017 03:34:41 pm

Yes that could well be the problem. I remember reading that the layer will not grow on the edge of a 90° corner and there are a lot of corners in a knurled part. I will give it a try and post my findings. Thanks Ken!

David Rice

4/13/2017 07:12:41 am

Ken,
I am trying to find the cheapest source of Sodium Bisulfate for Aluminum Annodizing. I believe I have a good source but it isn't 100% Sodium Bisulfate I think it is 94%. It doesn't mention what the other ingredients are. I got it from a Spa Store 8 lbs for $15 US. My question is if you have experience with BioGard's Lo 'n slo and if you know if the other 6% will be a problem in the Annodizing. I just don't want to waste $15 as I don't have a spa or swimming pool for another use of the PH reducer. Also do you know of a cheaper source of Sodium Bisulfate? Thank you for any help.

David

David Rice

4/13/2017 07:30:24 am

I looked up a Material Safety Data Sheet and it says 90-95% Sodium Hydrogensulfate, 4-10% Sodium sulfate (I'm not sure how that adds up to 100% but ... :-)).

http://hydropool.com/downloads/MSDS/bioguard/bioguard-lo-n-slo-msds.pdf

Ken

4/13/2017 03:34:10 pm

David,
All of the commercial pH down products have additives, and to my knowledge, none are reagent grade. Sodium sulfate is the least problematic side-product and it will not cause a problem. So, you found a good deal. You might want to compensate by adding a little more but even that should not be essential. Thanks, Ken.

Fernando

4/18/2017 03:40:48 am

Hello I prepared and implemented the setup you mentioned here. Everything went smoothly, but when the coloring process (after the DYE tank) was to rinse with cold water or to soak it in boiling water, it completely failed. The color is completely erased and flowing. The aluminum is turning back to its original shape. What is the reason for this?

Ken

4/18/2017 09:10:02 am

Hi Fernando,
Assuming that the dye is correct, and the dye is not coloring the metal says that the metal is not anodized. Of course, I don't know why it is not anodized but that is the case. Ken.

Paul

5/5/2017 12:01:36 am

Would this process work with 6060-T6 aluminum?

Ken

5/5/2017 10:45:06 am

Hi Paul,
The 6060 alloy is the same as any other 6000 series with respect to the al, mg, and si. The problem may come from the T6 which is a heat treatment to artificially age the surface oxide. If it is wrought, it could be a problem with any anodizing process. My thought is if you don't need the T6 go with a standard 6061. If you are already committed to this alloy, test before doing too much work. Thanks, Ken.

S.D. link

5/7/2017 12:24:25 pm

This is a great article for learning how to anodize aluminum safely. Thank you very much for the information!

Jack Spiggle

5/12/2017 04:05:50 am

Hey Ken,
First up, thanks to you for the amazing article and thanks to everyone else for sharing in the comments, really gave me the confidence to gather some supplies and try myself. I am following your method almost exactly using 6063 aluminium, a mystery aluminium cathode (which I will change out tomorrow morning having read some more comments) and a 18v .4 amps drill charger because my brilliant habby grade NiMH charger idea went bust when the charger figured out my apparatus want actually a battery after all =). Anyway, I am having some success as my part is taking some dye but it is very faint. The wire I am using to suspend the part however is taking brilliant colour? What gives? Tomorrow I was thinking of trying (as already mentioned) replacing my cathode with 6063, increasing the anodizing time and suspending the part with either makeshift "wire" cut from my 6063 stock or regular tin foil. Just wondering what your thoughts are on these ideas before I go try them and if you had any other ideas. Also (this may have been asked, Im still only part way through the comments) will leaving the part in the NaOH longer do anything except produce a deeper etch because I have been leaving my parts in for 10-15 minutes.

Again, thanks for the write up,
Jack

Jack Spiggle

5/12/2017 09:33:57 pm

I have since tried everything I proposed without success. Good new is I did figure out a lot. My NaOH just had to be replaced and now its working as expected and the parts are not anodising because I am not getting a solid enough electrical contact between my suspension wire and the part. When I connect the alligator clip directly to the part it anodises fine but thats not really an option for me because then half of my parts wont get anodised. Any suggestions?

Ken

5/13/2017 04:20:52 pm

Jack,
What you are describing is most likely (99.9 %) a simple connection, probably particularly because the wire was anodized. One solution that I have mentioned before is to make a aluminum wire paper clip and move it around every 10 minutes for uniformity. No need to increase etch just rinse and clean well before anodizing. Hope that this works for you. Ken.

Jack Spiggle

5/14/2017 01:47:24 am

Well, you were 100% right it was just a bad connection. I thought a simple hook would have provided enough contact but evidently not. Anyway, I did try the paperclip today but didnt like it (nothing against your precious paperclip XD) instead I tried your other method of bending the wire and jamming it into my part (as all of my parts had some sort of hole or slot). Using this method I successfully dyed a pocket clip for my keys, a pen casing and two aluminium washers (very wide washers but still incredibly thin, somehow I managed to get it to work tho). Another problem I ran into was that my first part took 6 hours to take dye (the first 4 hours it took almost nothing and the last two were very slow) which I thought was interesting having read others experiences with this step. Turns out I had not adequately dissolved the dye in my water having not heated it up at all for fears of sealing my part prematurely. Having fixed all of those problems I am now very happy with my results =D!! Thanks again for maintaining this amazing page!!!

Charles Small

5/15/2017 08:52:28 am

For the lead, as it is to be bigger than the piece being anodized, is it talking length, or total surface area?

Ken

5/15/2017 09:09:25 am

Hi Charles,
We are referring to surface area. Ken.

Bill Matthews

5/16/2017 06:07:55 am

Thank you for responding to comments and questions; I know both must be very helpful to your audience.
I'm going to use "pH Down" and distilled water for my electrolyte. What is the appropriate ratio of "pH Down, BY WEIGHT, to 1.5 gallons of distilled water?
Thanks for any help you may offer.

With my best regards,
Bill

Ken

5/17/2017 04:38:37 pm

Bill,
First, change gallons to liters. 1.5 gallons is approximately 5.6 liters. Then, as in the write up, the liter of course is 1000 ml and weighs 1000 grams. Each 800 ml, is (.8 liter). So, simply calculate how many 80's there are in 5.6 liters for the water. The remaining 20 % is powdered pH Down in grams which you can change to ounces or pounds as well. But remember, a 20 % electrolyte is a guideline and can be more if it is easier to work with. +/- 5 %. Hopes that this helps, Ken.

Bill

5/17/2017 07:49:24 pm

That should do exactly what I need to do. Thank you.

Bill Matthews

5/18/2017 10:03:22 am

For doing the math, this calculator has been very useful:

http://www.physiologyweb.com/calculators/percent_solutions_calculator.html

Richard Williams

5/23/2017 10:06:25 pm

G'day mate. I don't have all day to read through the comments but did you end up finding a good sealer? In the industrial processes we used alkaline salts. Have you ever tried borax?

Ken

5/24/2017 09:27:22 am

Hey Richard,
I have uses borax (sodium borate decahydrate) technical grade with mixed results. I continue to use nickle nitrate or just distilled water. Ken.

Ken

5/24/2017 09:48:33 am

Richard,
I meant to say nickle acetate. I missed my own error, XD, Ken.

Paul III

6/15/2017 10:58:43 am

I have four aluminum parts anodized black that need to be clear. Stripping the first three of black with the sodium hydroxide solution was a breeze.

The fourth part, also likely 7075, has been problematic. At first, it seemed nothing was happening. After quite a while it began to work...at first yielding a very "splotchy" appearance. Then, after hours of stripping and work with plastic and brass brushes, it finally came clean. However, unlike the first three parts, it seems black still leeches out of the aluminum as soon as it is placed in solution.

Is this a problem, was the part "deep anodized", I'm doing something wrong, or what?

Ken

6/16/2017 10:13:24 am

Paul,
My best guess is that it has more to do with how the part was sealed and how accessible the pores are. Although your problem sounds like the pores are really deep, it maybe in the dye. I would try to destroy the dye color by using either bleach or a solvent to remove the color after stripping with NaOH. Hope that this assists you, Ken.

Paul III

6/16/2017 01:35:13 pm

Thanks Ken,
It appears to be inconsistent metallurgy in the forged part.

All of the other parts are turning out very well...but this one had tiny holes open up in lines in the forging and the splotchy appearance returned after anodizing.

No warranty for this modification so a ($44) replacement has been ordered from a different supplier....we'll see!
Thanks again,
Paul

Greg

7/13/2017 02:21:28 am

Hi Ken,
I anodizing 4 pieces of 55mm thin wall aluminum tube approx 30mm long. They are being used for lens holders in some zoomable LED video lights I'm making. The main idea was to make the inside of the tube black so as the light wasn't scattered to much. I used very roughly the same mix of sodium bisulphate as you recommended and first tried with a 5 volt supply capable of delivering 500ma. Left it for about an hour then put it in the RIT black dye to the same strength you recommended. It didn't seem to be working much so I left it for ages and it still didn't work. Also I had just rested the parts onto a strip of aluminum on the bottom of the tray so perhaps there was a bad connection.
Anyway I decided to try again as I could see perhaps a small amount of color. I used the same electrolyte but made up some clips from aluminium so as there was less surface area, basically just the parts, and this time use a 12 volt battery charger capable of delivering 2.2amps. I got heaps of action from the anode and left it forabout 2 and a half hours. I also added about 3 or 4 more tablespoons of dye to the 1 liter jar I was dying in. Very rough and ready measurements. Anyway after sitting in the dye for an hour or more they were as black as the ace of spades aside from one which was perhaps a little further from the cathode. Anyway completely happy. I'm sure with a bit more fine tuning, proper polishing and more attention to the layout of the anodizing tray I could get pretty perfect results though it's more than good enough for my purpose.
cheers Greg

Greg

7/13/2017 02:26:18 am

P.S. I didn't use distilled water. We are on tank (rain) water. It goes in to a concrete tank then through poly pipes
Greg

Tim

8/28/2017 01:42:49 am

Hi Ken,

Thanks for sharing your findings! What is your experience using oxalic acid as an anodizing electrolyte for aluminium?

Best,
Tim
Tim

Ken

8/29/2017 10:37:27 am

Hi Tim,
I have worked with oxalic acid as well as malic acid but both are a bit difficult. First, the voltage needed for oxalic is much higher, 100 to 200 VDC. The anodized surface is very highly colored, mostly a pale yellow which interferes with dyeing. The surface is hard but the process is just not very easy or worth pursuing as far as I can tell. That is my limited experience with oxalic and hope that it helps, Ken.

Tim

8/29/2017 01:09:08 pm

Hi Ken, thanks for your reply, your answer it is most helpful. I don't want to over complicate the process. I will just go with the suggested Sodium Bisulfate instead.

James

10/4/2017 10:44:57 am

Hi Ken, I am trying to anodize aluminum horseshoes. They are hard, bright, smooth, 19xxx aluminum. The dye will not take. I need to desmutt?? Is there a safe way??? Thank you.

Andrew

11/20/2017 12:51:45 pm

So I have went threw and made up all my jars for anodizing. My lye bath at ~2% mix and then my acid bath up at 40 grams of of ph down sodium bisulfate 93% active to 160 grams of water which is 160ml. I have not been able to get my power supply to put any amps out at 15v. I am using 2 pieces of flat stock that stocks up out of the solution so I am not using any wire to hang my work piece.

When I ohm out the solution it is ohming at 2.4m ohms. And my leads are about 1” apart. I keep seeing that the solution should be much lower down into the single digits. I think this is my issue but what is causing this high reading.

Ken

11/21/2017 10:10:48 am

Hi Andrew,
The solution that you have is clearly not sufficiently electrolytic. Based on some quick math I would guess that the pH is close to 5 or 6 instead of 1. Perhaps the container was not as stated and there is simply not enough sodium bisulfate. Try adding a lot more and re-check the resistance. Hope that this helps. Ken.

Jeff

1/18/2018 12:35:31 pm

I am having the same problem. I have a ph meter. I have taken the ph down to 0.8 and up to 2. My power supply is adjustable. 12 volt is around 0.02 amps and at 14 volts it is around 0.04 amps

Dudley Baker

12/7/2017 01:06:02 pm

Hi Ken
Thank you for keeping this forum open and running. Ok first off i am using a battery charger for my power supply, last night was my 1st attempt at the anodizing process. Well it failed but i am positive i will be successful in time. Why would the cathod stop bubbling after about 20 minutes or so.

Ken

12/7/2017 04:09:39 pm

Hi Dudley,
I am assuming that you have the polarity correct and if so, it sounds as if the connection to the cathode may be intermittent. If you are running 12 VDC it may be too much for the size of the part on the anode and can educe the hydrogen bubbles at the cathode. Is there any chance that the cathode has been clear anodized as this would reduce the current flow. Is it also as large as the piece at the anode? Ken.

leo

12/16/2017 11:05:07 pm

Hi,
I've started the process of doing my own anodizing rather than have it done by professionals. My setup is as Ken's suggestions.

Can someone explain me how to get a shine on clear anodized 6061 aluminum as my parts come out mat after the anodizing process? I'm looking for a product or a process, not into buffing. The poeple who used to anodize my parts were probably using a chemical product.

Thanks
Leo

Ken

12/19/2017 04:07:28 pm

Hi Leo,
I have two questions and a comment. First, are you etching the parts with NaOH solution, and second, are you sealing with either boiling water or nickle acetate? It sounds like an index of refraction problem. There are some coatings that will provide a luster but let's see what the problem is, Ken.

Leo

1/15/2018 03:03:23 pm

Hi Ken,

Sorry for late reply. I've posted a long message before Christmas but it doesn't seem to have gone through and I've put the anodizing test aside so I didn't follow. But I'm starting back the process, I need good results. Got a bad batch again from my supplier last week. :(

I was using NaOH at first when I started this whole process. I experimented on many sample temperature and etch time. I stopped doing the etch part as I found it modifed too much the surface finish and lustre.

I'm sealing with boiling demineralized water.

After doing more tests, seems the mat finish is caused by the anodizing step. I'm using the PH- solution. Could this electrolyte solution cause a mat finish compared to sulfuric acid?

Thanks,
Leo

Joacim

1/10/2018 02:03:53 pm

Hi Ken! Great step by step guide!

However i have some unceirtantice about the mixing of the ph down. I want to use just 400ml of destilled water. How much ph down in grams do i need to get a good mix?

Thanks in advance

Ken

1/11/2018 09:34:13 am

20% of 400=80 grams.

Joacim

1/14/2018 12:39:32 pm

Thanks alot. The ml and gram had me abit confused :)
Gonna try it out soon and get back how it went

Ken

1/16/2018 05:04:53 pm

Leo,
Both pH down and H2SO4 cause pores to form and to the degree of the size of the pores, an index of refraction problem. Both will reduce the luster and it is inevitable unless you go to hard anodizing. Sorry it is just the nature of the process, Ken.

Leo

1/17/2018 03:06:23 pm

Hi Ken,

I understand and it makes quite a lot of sense. I'm guessing the sealing brings back some luster. The plating company I'm actually doing business with uses a degreaser, sulfuric acid and common boiling water to seal my parts. My parts shine as much as before I send them (600 grit), if not more. The test I'm doing here are far from being luster. In the same conditions, If we were to compare PH down to sulfuric acid, do you have an idea on how they would differentiate on refraction? Thanks

Ken

1/18/2018 09:52:41 am

Hey Leo,
One of the first things that I did when developing this process was to compare the surface finish using a microscope. Although I am unable to quantify percentage, the H2SO4 was definitely more aggressively attacked. Having said that, there are several variables that may reduce the aggressiveness like concentration, voltage, current, and time. But, that is my general thought. Ken.

Leo

1/18/2018 07:48:42 pm

Hey Ken,
My understanding is that from your process, it is more ecological and therfore less agressive on the parts unless boosting other variables. I noted that everything matters and all parameters are important to consider, any small change affects the results. I will test the reflectance with my gig sulfuric acid and hopefully be able to reproduce the expected bright finish.

Thanks for all your help, sharing your work on the internet is what got me started. Cheers!

Rumaldo G

1/28/2018 12:03:46 pm

Can I use Hydrochloric acid as a substitute for anodizing?

Ken

1/28/2018 03:41:52 pm

Rumaldo,
HCL will etch and destroy aluminum. Aluminum reacts with hydrochloric acid to produce aluminum chloride and hydrogen gas. 2Al(s) + 6HCl(aq) -> 2AlCl3(aq) + 3H2(g). Ken.

Woody link

2/15/2018 06:48:20 pm

Hello Ken,

Thanks so much for this option in anodizing! It's been working perfectly! I have a question though. Can I reuse my anodizing bath, dye bath, and etch bath for future pieces? Maybe at least one or two additional times? Is there a time frame for these materials that then go bad beyond a certain point?

Ken

2/16/2018 09:59:42 am

Hi Woody,
All three are reusable but with some observation. The etch and dye solution will fail to etch and the dye solution will be less saturated but both can be used several times. The anodizing solution can be reused but it depends on the size of the parts and the volume of the solution. The best way to predict efficiency is to monitor pH with paper test strips or pH meter. The strips are available online and at most pet stores that sell fish. Check the pH with a fresh batch and watch for changes over time. As the pH approaches 3 or greater, its time for new solution. Ken.

Jeff

3/20/2018 02:21:30 pm

I have been trying to anodize a 1" round spike. 1-1/4 long. It has a 8-32 tapped hole in it. I am successful in anodizing the part. It just leaves a un anodized area above the screw hole as wide as the screw hole sometimes. I picked up a few nylon screws and plugged the hole, but it is still the same. What am I doing wrong?
http://i66.tinypic.com/foitdh.jpg

Ken

3/21/2018 11:11:42 am

Hi Jeff,
The only reason I can see is that during the preparation something is being left behind that acts as a resist. It really does not make sense. One possible experiment would be to use an aluminum screw as either the primary or secondary anode connection. BTW, nice job! Ken.

Jeff

3/21/2018 12:46:39 pm

I have polished them in the lathe. Then decrease, rinse, sodium hydroxide, soak and rinse.I use latex gloves in every step. I use a titanium anode on the inside. I have done several and they all come out the same. I even used a nylon screw in the hole. I will try the aluminum screw in the hole.

Rod

3/23/2018 02:01:21 pm

Is there possibly a shadow between the Cathode and the part?

Maybe add an extra Cathode?

Jeff

6/11/2018 05:22:26 am

No I don't think so. I position the hole in different location. Left, right, top bottom. I will try an extra Cathode. Thank you for the suggestion.

Jeff

3/26/2018 05:29:27 am

I am using two aluminum strips running top to bottom and the length on each side of my tank. I dip the in sodium hydroxide and sand them each time I anodize. I also use an air pump to circulate the anodizing bath. I still need to make a few aluminum screws to fit into the tapped hole. I also want to thank you for all your help. I put off anodizing for years because I didn't want to deal with the battery acid. Your process is so much safer, cleaner, and easier to do.

Jack

3/28/2018 11:58:27 am

Hi Ken,

I set up a system in my garage about ten years ago to clear anodize electronics panels and chassis. Most of my parts are cut on a CNC mill and/or lathe, then scuffed to produce a brushed appearance. Other than the fact that I was never able to achieve a really bright finish, the system worked well.

I've gone through a period of inactivity the last few years, and now I need to rebuild the system. It hadn't occurred to me that other chemicals might work for this, so I'm wondering if I should abandon the sulfuric acid method in favor of something safer. I'm starting from scratch with new tanks (coolers) and chemicals, so now is the time to make a decision.

Can you give me some idea regarding the hardness and appearance of sodium bisulfate anodizing compared to sulfuric acid? Again, I'm only interested in clear anodizing, so any issues related to dyeing are not important to me.

One more thing - Caswell used to sell an additive to prevent rising bubbles from bursting too vigorously and spattering acid around the tank. Do you know whether this is compatible with the sodium bisulfate solution? I use a homemade bubbler for agitation, so this might be an important consideration.

Thanks for maintaining this site!

Ken

3/28/2018 04:41:03 pm

Hi Jack,
Since sodium bisulfate is a half-salt of sulfuric acid the hardness is pretty much the same, at least in my tests which are hard to quantify without some better analytical tools. The main advantage of my process is the safety factor in transport and storage. My sense is that if you are comfortable with sulfuric acid I wouldn't abandon it Especially if you already have the working parameters. As far as the Caswell anti-bubble I have no useful knowledge but perhaps other readers do. Good luck and thanks for the questions, Ken.

Martin Gaudet link

4/26/2018 05:55:36 pm

Ken,
Is that ever cool! I just anodized my first part. It is 6061 aluminum anodized in straight battery acid (1.265s.g.) which I got from the auto parts store, at 11 volts and 1 amp on a part with 8 sq. inches area for 50 minutes. The tank I built is lined with lead sheet which I wrought from a 25lb lead brick using my 450 ton forging press. I then used liquid black RIT dye at 140 degrees F for 10 minutes, followed by a 45 minute boil in a 1/2 gallon of water and 5 vitamin C tablets to pickle the pores closed. I got a dark bronze onto black. A knife skates off the surface, so I know the oxide film is robust and the dye is bound underneath it.
The question I have is this: before anodizing, I flashed the part in the acid for about 3 seconds with reversed polarity and 20 volts, and it nearly boiled the acid with bubbles! Is that a recognized way to blow off the dirt and prepare the surface prior to anodizing?
Thanks, I really like your blog!
Martin

Jack

6/11/2018 12:30:57 am

Thanks for your reply, Ken. I will stick with the sulfuric as you suggest, at least for now.

I find Leo's comments above to be very interesting. Work that I polish to a mirror finish always emerges from the tank dull gray. It seems Leo has the same problem. What surprised me was his statement that work from his commercial service provider is lustrous. It sounds like the company is using the same steps I do. Desmut briefly (still shiny after this step), anodize for a thickness of about 0.5 to 1.0 mil, then rinse and seal in boiling water. I just don't understand how my process can be creating this issue. How do finishers get the bright clear anodized shine seen on work like home electronics panels?

Jack

6/16/2018 12:09:37 pm

One thing I haven't seen discussed here - can the solution contain both sodium bisulfate and sulfuric acid? Will the acid react badly with the bisulfate or the additives that might be contained in a pool product?

Ken

6/20/2018 03:44:25 pm

Jack,
It is inadvisable to mix the two as it will degrade the sodium bisulfate. Ken.

Jack

6/16/2018 02:22:49 pm

Ken, sorry to clutter your forum with so many questions. I'm reconsidering whether to use sodium bisulfate for the new setup, and there are a few details I'm trying to work out.

First, I was reviewing my notes from last time, and it appears I mixed 2 gallons of battery acid from the auto parts store with 6 gallons of distilled water. Can you confirm whether I have the ratio correct for bisulfate - 6 gallons water would require 12.5 lbs of sodium bisulfate?

Also, how do you calculate the percentage that's been achieved when it's mixed with water? The bisulfate is measured by weight, but the water is volume.

Related to this, do you know what the equivalence might be regarding sodium and battery acid? In other words, If I buy 10 lbs of bisulfate, how much acid wold be required to "make up" for the remaining 2.5 lbs? I'm asking this because I have about 2 qts of acid left over from the previous operation a few years ago.

Finally, are calculations like the 720 rule applicable to sodium bisulfate? Does any of that need to be modified for a bisulfate solution?

Thanks again for your help!

Ken

6/20/2018 03:49:58 pm

Jack,
It is much easier than that as we make a 20 % solution. For 100 parts there are 20 grams sodium bisulfate and 80 Ml water which is 1 gram per Ml. That should make it easier for you to calculate. And yes, the 720 rule is the same. Ken.

7/2/2018 10:36:20 am

Good morning and congratulations. The seoh04 Is the same as it is to seoh.

7/2/2018 01:50:00 pm

sorry I wanted to write.Good morning and congratulations. The naoh04 Is the same as it is to naoh.what is the meaning of the number at the end of the word (04 ??????)

Ken

7/2/2018 05:14:57 pm

gs,
The 04 refers to the molar mass but is seldom used in most chemicals, Ken.

Val

7/6/2018 03:16:45 am

Hi K,
Thank you for this tutorial.
I tried this with a 12V battery and it didn't work at all. However, When i tried with a sulfuric acid solution it did work although the result wasn't satisfying. But it made a lot of bubbles this time.

I used NaHSO3 instead of NaHSO4. Can it be the reason of the problem? I looked up online and didn't find any difference between the two.

Also. I'm considering asking a factory to do the anodizing part for me and picking my pieces at home to do the dying part myself. Is that possible? Or do the aluminium need to be dyed as soon as it's anodized?

Thanks for your help

Ken

7/9/2018 10:10:53 am

Val,
There is a significant difference between the bisulfite and the bisulfate and the bisulfite will never work as there is no half salt of H2SO4. The sulfuric acid that you used probably didn't work as there are many variables like voltage, current, temperature, and time. It takes patience for either process. As to the dyeing, if you are going to have the anodizing outsourced it would be best to have them dye as well as it is the most expensive aspect to get professional results at home. Ken.

Val

7/15/2018 11:44:09 pm

Thank you so much for your help! I will try again with H2SO4 them.

Jack

7/10/2018 06:55:43 am

After considerable online research, I decided to use sulfuric acid after all. What changed my mind were a number of posts discussing the fact that the bisulfate is depleted during use. That would have added one more variable to my process, as well as an additional area of maintenance.

I have to say, the system is working even better than when I used it a few years ago. Back then, I was using the homemade power supply that also powers the stepper motors on my small CNC mill. Now I have a dedicated power supply for this (also homemade), along with a Variac to control output voltage. In addition, I built a variable 10 Amp current controller. Now I don't have to constantly monitor and manually adjust the current from start to finish. I can just set it and walk away - really nice!

One thing I noticed - it seems to me the dulling effect I mentioned earlier may actually be occurring during the sealing process (I use distilled water for this). I need to confirm this effect with two work pieces side by side, one sealed and one not. I'll report back if this turns out to be true. So far, the technique to achieve a truly shiny surface has been elusive.

Ken

7/10/2018 09:57:59 am

Jack,
Glad to see your success but all electrolytes become depleted during electrolysis, even sulfuric acid. Best check is with pH. The sealing process dosn't care if the water is distilled or not as it is the heat that seals the pores. The dullness can be attenuated by polishing the aluminum before anodizing. Ken.

Jack

7/10/2018 07:25:46 pm

I guess this is a case of misinforming myself. :) Isn't it strange that none of the DIY anodizing sites like Caswell discuss the issue of acid depletion? At any rate, from reading your blog, it appears I should target a ph of 1-2, or a hydrometer reading of 1225-1250. Is that correct?

Several years ago I painstakingly polished two 6061 panels approximately 14" x 5" to a mirror shine. They were immediately dulled by the anodizing process. I'm still looking for the solution...

Ken

7/12/2018 10:55:27 am

Jack,
I would suggest pH as the better method as it is not temperature sensitive. Th pH paper is fine and your numbers are correct. As to the dulling I have no helpful knowledge. Someone knows what brightener is used but it is out of my general awareness, Ken.

vicky

7/14/2018 12:08:58 am

Would baking the Al at 500 degrees F for, I don't know lets say 15 minutes then immediately putting it into the anodizing bath help the anodization of the Al. My thinking is that by heating the Al the Al will become more pliable or softer which in turn will help the anodization solution adhere better.

Ken

7/14/2018 10:09:02 am

Hi Vicky,
Since the mp of aluminum is greater than 1200 F, heating to 500 or so will not soften it but will make the oxide layer harder. While some materials work better when wet, this is not one. It will form the micro pores without any other treatment than mild etching of the oxide layer. Thanks for the question, Ken.

Jack

8/31/2018 10:08:43 pm

I only anodize clear (no dye), so the overall process is relatively simple and forgiving. Nevertheless, I sometimes encounter unexpected results from the sealing process. Is boiling water a necessary component in this? Can the freshly anodized aluminum be baked instead?

Ken

9/1/2018 03:43:46 pm

Jack,
Baking will not close the pores so boiling water is necessary, Ken.

Jack

9/1/2018 07:08:54 pm

Well, that's disappointing. Sure wish I understood the process better. I get odd results sometimes after sealing, such as a haze that has to be polished off. Once, it produced water spots that couldn't be removed. I had to strip the part in sodium hydroxide and anodize/seal all over again. I'm getting ready to do another panel this evening. Wish me luck!

Jack

9/3/2018 03:37:55 pm

OK, I learned something today. The piece I just finished is a half-inch thick panel about 10" x 4". It came out of the anodize bath in beautiful condition, but it looked awful after sealing. The haze I mentioned above was everywhere, much worse than before, a whitish film that was very difficult to polish off. In addition, there were several shiny spots on the surface where it appeared the anodize layer had been eaten away (before I started polishing). This was particularly prominent on several small-radius edges, where I assume the layer is thinner than elsewhere. Running ohmmeter probes over the surface confirmed the insulating layer was gone in those areas. Even on the face, which looked OK visually, the insulation was intermittent as I wiped the probes across the surface. Using a beeper, the tester would "crackle" as I moved the probes around certain areas.

This is the fourth panel I've done since coming back to anodizing and rebuilding my system. The first two were somewhat smaller, and they were sealed in a Teflon-surfaced pan using distilled water. The third panel was larger like this one, and it was the first to show the hazing issue. Because of its size, it had been sealed in a large stainless tub. Considerably more water was required than previously, so I used tap water. This fourth panel also used tap water, but I left it in the boiling water much longer. Where the earlier panel had been in about 1/2 hour, this one was about 1-1/2 hours.

This all made me wonder if the problem might be my tap water. So, I completely stripped and resurfaced this panel (ugh), then re-anodized and sealed in distilled water. The panel now appears perfect, there is no sign whatsoever of haze or surface loss, and it does not conduct.

I know you've said distilled water isn't necessary for this step, but it seems at this point that might not be entirely correct. I didn't have this issue the last time I was anodizing (several years ago), and back then I used distilled water for every step of the process. It was only after reading through this blog that I came to believe sealing in distilled water would be a waste of money. I have no way to know why this occurs, although I'm suspicious of my water softener. It's said they put small amounts of salt into the water, and that would certainly explain the symptoms I'm seeing. Regardless of the exact cause, I think it would be prudent for other readers not to make assumptions or to overlook this aspect of the sealing process. At the very least, anodize and seal a piece of scrap before submitting your prized work.

Rod

9/5/2018 08:21:03 am

Water Quality varies greatly from town to town.
The level of impurities is based on what is "ACCEPTABLE" as a standard not what you would find in distilled water which should be perfectly pure.
Lead, Chlorine and other contaminants in different Parts/Million could impact your sealing process.
I agree with your statement Try it on a sacrificial part 1st.

Ken

9/11/2018 10:08:18 am

Jack and Rod,
Good information and based on the variability of tap water a small test would be wise. We all learned fro this shared information. Thanks, Both, Ken.

Jeff Thompson

9/25/2018 01:47:20 pm

Had something happen. I have been anodizing harley head bolt covers I make. I have done a few colors and it has been working well. I had someone get in contact with me. I colored 4 of them Blue AD. Two of them had begin to fade. Any idea why?

Thanks,

Jeff

Ken

9/25/2018 03:39:26 pm

Jeff,
Two possibilities come to mind right away. Either the pores were not completely formed or not sealed. Check insulation with a meter and re-do with fresh electrolyte. Ken.

Jeff Thompson

9/28/2018 08:23:39 am

Thank you. I will change the electrolyte. I keep it at 1 ph. I bought a ph meter. I anodize these is a batch of 4 so that all match.

Craig

1/13/2019 12:59:52 pm

Hi Ken, thanks for the great information. I tried this over the weekend and had some reasonable success.
One odd thing I found is that I had two identical small parts in at the same time, both of which had been prepared the same, and one took the color far better than the other. I'm pretty sure that I also had the same electrical connection. Any thoughts?
I've been using small aluminium craft wire, probably about 1mm diameter, perhaps I need to use something heaver?
I also wanted to ask if the Sodium Bisulphate solution needs to be new for each new run. Does it become dilute following the anodizing process?
Thanks again for the method.
Craig

Jeff Thompson

1/14/2019 10:19:12 am

I have the same problem. I will anodize 8 pieces sometimes I get all 8 the same color, other times 1 or two will be very light compared to the rest. I take great care to clean and prep all 8 together. I am using a titanium holder for all 8.

Ken

1/15/2019 10:41:39 am

Jeff,
The comments for Craig also apply to your problem, Ken

Ken

1/15/2019 10:33:26 am

Craig,
A heavier wire would be useful to carry the current but two other possibilities exist: Distance from the cathode and stirring the electrolyte periodically to distribute the coverage. The electrolyte can be re-used if the pH remains at 1 or 2. Use a pH paper to test, Ken.

Mike P.

1/13/2019 08:16:32 pm

Hey Ken - thank you for taking the time to create not only this website but the videos on YouTube - both have been a good start for anodizing for me. I've been working on some titanium anodizing only to find out that the part I was trying to anodize wasn't actually titanium!

I'm a ring maker and thought adding anodized colors to my line of aluminum rings would be great, well it would be if I could get it working.

I live in Canada so some of the brands that you discuss, mainly the ph down, aren't available to me locally. I used a brand called Aquarius pH Reducer. The MSDS shows it's Approx Conc % is 60 - 100 and when I read through a little more I see something that mentions pH of 1.4 (1% solution).

Long story long - I've tried anodizing a ring twice now, once in red and once in blue. I used a batter charger, 12V 2A, for 1.5 hours with a 1/2" wide 4" long strip of aluminum for the cathode and a 6" long piece of aluminum wire wrapped around the ring but am not getting any color to take during the soak in RIT. I tried a third time with 3 9V batteries for an hour and still no color.

The only step I didn't take was the soak in Draino - is this necessary? I did polish and clean the ring with alcohol prior to anodizing...

Do I need to make a stronger solution? Does the ring need to be cleaned with draino? Any assistance anyone can offer would be greatly appreciated.

Mike P.

1/15/2019 07:37:38 am

A quick update and another question...

I was able to successfully anodize a ring - I had to use the Liquid Plumr and soak the aluminum for about 15 minutes. Fairly happy with the outcome but need to hear from others...

I tried red, which I have now read that blue and red are the most difficult colours to anodize, and my ring came out pink. Any success with anodizing red? Do I need to switch to Caswell colors to get red and blue to come out?

I'm going to try a green ring tonight.

Ken

1/15/2019 10:45:50 am

Mike,
I would definitely suggest Caswell, Ken.

Jack link

1/15/2019 08:31:35 am

I'll preface this comment by stating that I don't dye my work. However, even when anodizing clear, it's painfully obvious when the process hasn't worked. My first anodizing system had all the various options in terms of preparation, including a degreasing step, Caswell desmut wash and a weak sodium hydroxide bath. The latter is the active ingredient in Draino. After using the system for some time, I took a hiatus and pursued other interests for a couple years. By the time I set the system up again, my work area was considerably more crowded, so I decided to only use the bare essentials. I can tell you now from experience that if the degrease step is properly completed, nothing else is required. I start with regular dishwashing liquid and finish with a so-called "industrial" cleaner in a spray bottle (Home Depot or Lowes). I clean the items by hand, then with a toothbrush and rinse thoroughly in tap water. Finally, the pieces go into a small plastic tube filled with distilled water until I'm ready to connect them to the system (usually only 10-15 minutes). All of this is done while wearing latex gloves, and I wash the gloves in dishwashing liquid after I put them on, before cleaning the parts. When the degreasing is complete, water should "sheet" off the parts. If it beads anywhere, they're not clean. I think if you do this, you'll find further cleaning or surface prep to be unnecessary.

Mike P.

1/15/2019 08:42:47 am

Thanks Jack! I'll give this a try on my next round.

brettG

1/29/2019 12:13:25 am

Hi Ken Great thread & thanks also to everyone whos contributed in the comments with helpful advice.

Can I ask a quick question about when it comes to mixing up the Sodium Bisulfate & Distilled water.

So I added 4ltrs of distilled water into my container then weighed out 1000grams of 92% dry Sodium Bisulfate.
Mixed Well as suggested in the write up but most of Bisulfate just sits on the bed of the tank like sand no matter how much i stir.

Has anybody else had this problem and what would you suggest ?

water temp around 48f , could I heat the solution with a aquarium heater to around the 65 - 70f ? would this help disolve it.
Being usually for swimming pools I thought you wouldnt have to the above but I am stuck

thanks

Ken

1/29/2019 10:10:02 am

Sodium bisulfate is very soluble in water. 30 ml/100ml water at 25C. My best guess is that the material is not 92% but has other materials. Best way to check is with pH paper and test for 1-2 pH. Then filter out the impurities. All pH down products are not created equal! Hope that this helps, Ken.

brettG

2/6/2019 06:05:53 am

Hi Ken thanks for the response, I took what you told me on board and tested my solution which in result was in the ph range of 1-2,

So used an old set of the wifes tights over a bucket and strained out all the whites crystal salts to give me a pure clear solution.

thanks once again

Jeff Thompson

4/10/2019 05:51:58 am

Been anodizing for a while. I have run into a problem I can't seem to solve. My parts are coming out spotty. Some areas are not anodizing well. Some lose their dye when I try to seal them. I clean them well. Actone them, then a good rinse, them a decrease in how water, rinse them, then etch them. I even ordered some desmut and tried that. I have changed my tank fluid. Even changed brand of Sodium Bisulfate. Any ideas?

Jack

4/10/2019 09:00:06 am

A few things I can think of...

First, the last step in cleaning should be a scrub in a non-petroleum spray degreaser (soap/phosphate based). Water should "sheet" off the piece in the final rinse. If it beads anywhere, the piece isn't clean. And of course, the piece should be handled only with rubber gloves at this stage.

Also, on the off chance something is wrong with the etch bath, try anodizing without that step. In my experience, etching isn't a prerequisite to achieving uniform anodizing.

Are you using agitation during anodizing? The bubbles that form on the surface of the work will insulate those areas from the process.

The last part of the equation is the specific alloy. If it has a high silicon content (like diecast aluminum), results won't be good.

Jeff Thompson

4/10/2019 12:32:39 pm

I use simple green in hot water after the acetone. I make sure the water sheets off. I have tried agitation and non agitation. Same results. I am using 6061 T-6 on all my parts. The only thing I have not tried is the etching part. I have etched each time. I will try it without etching. I use rubber gloves anytime I need to touch the part.

Thanks,

Jeff

Jeff Thompson

6/14/2019 12:56:27 pm

I anodized a set of head bolt covers blue. Sent them to a guy. He bought them in January and opened the box in May. The color had faded out and it look almost like it wasn't anodized. Does anyone know why?

Ken

6/14/2019 04:50:09 pm

Jeff,
There are several possibilities. The pores were not deep enough, could be the material, or the pores were not well sealed. Hard to tell from here, Ken.

Jeff Thompson

6/15/2019 08:26:00 am

I use the same process for those as I have on others. I did have a problem with the Sodium Bisulfate. The Clorox brand was contaminated and I would have to filter it, everytime I used it. Finally Drove an hour to the next town to buy HTH brand. It is the only variable that I can think of. But with the Clorox brand they would take color and seal. I also use Nickel acetate to seal them with. Would posting a pick help?

Jack

6/14/2019 06:11:01 pm

January to May is a long time for a customer to wait before inspecting parts. Are you sure they haven't been used? What type dye did you use?

Jeff Thompson

6/15/2019 08:17:46 am

I am using Blue AN from Caswell. I thought it was a long time also. But it is for a Harley and he lives in the Dakota's. I have been making these for a few years. Started anodizing them about a year os so ago, when I found Ken's process(Thank you so much Ken). These are the 1st ones I had fade like this. They sit on the head bolt of a Harley engine. Any suggestions?

Jack

6/15/2019 02:12:57 pm

Jeff, have you contacted Caswell about the problem? It might be worth asking whether there's a maximum temperature rating for this dye, or if they've changed something recently. Harley heads get pretty hot. Meanwhile, I'd handle the customer end professionally and make it right (if you haven't already). It might take some time to determine what went wrong.

Jeff Thompson

6/17/2019 06:04:17 am

Hi Jack, The customer has been great. We are making a new set for him and getting them out soon. I have bought a slightly different shade of Blue. It seems the Blue AN is no longer carried by Caswell. I have asked the customer to send them back, once he receives the new ones. Si I can contact caswell. As with everything my wife and I sell. We stand behind everything 100%. We also have decided to start applying a coat of high temp clear paint to help protect the color. Also. Is blue a difficult color? I dyed 3 different sets over the weekend. 2 blue and 1 red. 1 set of blue washed out when I sealed it. All of the Aluminum in 6061 T-6. All of them were from the same bar. This is not the 1st time this has happened. One last question. Voltage. Is higher or lower voltage better. I run most all parts at 14.5 volts. I have one part I run at 12 volts, because it is thin and anything higher than 12 volts burns a hole in it.

Jack

6/25/2019 08:43:50 am

Jeff, it's been my experience that consistent anodizing results require constant current, not constant voltage. There was a time when I was using a relatively unsophisticated variable-voltage supply. I added a current meter, but had to constantly monitor and adjust the voltage to maintain correct process current. I have since built a constant-current adapter for the supply, and life is much easier. Current is set once, at the beginning of the process (according to the area of the parts), and I can just walk away until sufficient time has elapsed. I would encourage you to buy a constant-current power supply before going further with this work. There are a lot to choose from at reasonable prices on the big auction site.

Jeff Thompson

6/26/2019 10:24:44 am

I spent a few dollars when I started, and got a somewhat nice power supply. 30 volt 10 amp with fine tuning on both voltage and amperage. I use titanium wires and rods on all of my parts. I sand and test the connections with a meter on each part. When I do anodize. When I lower the voltage, the amps decrease. When I increase the voltage, the amps increase. I set the amperage above what the calculator says. It seems to never reach the suggested amperage.

Jack

6/27/2019 08:20:34 pm

Jeff, how are you determining the desired current to set? I use the 720 rule, and it has worked well.

https://www.caswellplating.com/720.html

Generally, in a system where the power supply is controlling the current correctly, voltage will initially be very low. As the oxide layer on the part grows, the aluminum becomes less and less conductive, and voltage will increase (automatically) as required to maintain the same current. Voltage will be highest near the end of the run. In my case, using sulfuric acid, voltage usually doesn't exceed 15-16V using the 720 rule.

If you aren't able to achieve the desired current even at 30V, either the anodize solution isn't sufficiently conductive or there's an error in your calculations. Under normal home anodizing conditions, I would expect 30V to burn the parts.

Jeff Thompson link

7/1/2019 11:26:44 am

I have put up the website my wife and I use to sell some of the parts we anodize. Here is an example. I had to anodize some washers for a customer. The washer is 1 inch O.D. 0.250 Thick and 0.375 hole. I get 1.8408 surface area. I do 6 of them at a time 11.0448. The online 720 calculator says 0.46 amps at 15 volts. 120 minutes to create 1 mill anodized surface. I use a regulated power supply 30 volts 10 amps. Titanium rods. I sand the rods each time I use them to make sure they make good contact. Mounted to a 1 inch stainless steel bar. I use aluminum wire going to each rod to insure equal power. I set the power supply to 0.75 amps 15 volts. I get 0.22 amps at 15 volts. So I left the parts in 280 minutes. I did several sets and the amps stayed the same each time. I know I am missing something. I have tried two different power supplies to make sure it wasn't that. Any suggestions?

Jack

7/1/2019 10:06:51 pm

I ran your numbers on my 720 calculator and got the same results (I'll take your word for it regarding actual area). These numbers occur with the calculator set for a current density of 6A per sq. ft.

My first thought is that you might be setting up the power supply incorrectly. What the calculator is telling you is that 0.46A for 120 minutes will achieve a 1 mil depth. These are the important parameters. It is also telling you that the process can be expected to need a peak voltage of 15V during the cycle. This number provides a means to determine whether the system is behaving in a reasonable manner, but it is only approximate. It will vary as the power supply compensates for variations in solution resistivity, oxide depth and even the resistance of the connecting wires. It doesn't matter much if the voltage climbs to 20V, or never rises above 10V, as long as the power supply maintains 0.46A for 120 minutes.

To set an adjustable-current supply, you should first adjust the voltage to about 20V or so with nothing connected. This sets the ceiling and should ensure that you have sufficient voltage throughout the cycle to maintain the necessary current. The supply will adjust this downward as necessary during operation. With the voltage set and the current control set to zero, connect the supply to your work. Raise the current control until 0.46A is registered, then let it do its work for 120 minutes. If 0.46A can’t be accomplished, something is wrong.

One thing to note is that multiple small pieces can create problems if they're not all making good contact. There's no way to monitor the current into each piece individually, and the supply will simply raise the voltage in an attempt to compensate. This can create “duds” in an otherwise good bath of parts.

Let me know if you have questions about any of this.

Jeff Thompson

7/13/2019 09:27:54 am

Thanks Jack for the information. I am going to try your power method this weekend. It has got me to wondering something. I use aluminum for my anode. I really don't like dealing with lead. Would that have to be factored into the calculations? Is there something better than using aluminum for the anode beside lead. I also sand the anode each time I use it to make sure it is raw aluminum.

Jack

7/13/2019 12:19:58 pm

I use aluminum electrodes in my system primarily due to concerns relating to disposal of lead and lead-contaminated solution. This is a serious safety hazard for landfills and municipal water treatment. Toss that stuff into the sewer system today, and you might be drinking it tomorrow.

The only functional difference between lead and aluminum electrodes as far as I know is that aluminum slowly dissolves into the bath. Even when not in use passing current, it will slowly disappear. This makes the bath more conductive over time, requiring the solution to eventually need replacement. My original tank used electrodes that were permanently submerged, and they totally dissolved during a period of inactivity that lasted about two years. Now I have the two flat electrodes attached to a frame that I lower into the tank only when needed. When a job is done, I lift the frame out of the tank and spray everything down with distilled water. Then I close the lid and set the electrodes on top.

There's no reason to sand the electrodes. They'll always conduct well unless you accidentally reverse the voltage and anodize them. :) You could prove they're good by testing the surface with an ohmmeter, but I've never had to do that.

Incidentally, my most recent experience (a few posts down from this thread) has made me realize the importance of centering work between the electrodes. I also now believe parts must not be positioned so that any of them create shadows on the others. They must all be lined up in a row parallel to the electrodes for an even layer of anodizing to be created.

Let me know how everything works out.

Jake

6/25/2019 06:51:14 am

Hi Ken!

Thanks for your tutorial. I am at a bit of a loss when it comes to the power source. I have 27 square centimeters I need to anodize and if my calculations are correct I would need about 0.4 Amps. Can I use a wall wart with 5V voltage which gives 0.5 Amps? Or would it be better to go with a laptop charger at 15V and 4A? What would be ideal?

Jack

6/25/2019 08:53:05 am

Jake, the current drawn by the part being anodized is a function of A) the applied voltage and B) the resistance between the part and the negative electrode (through the solution). The speed and depth of anodizing, and the amount of heat generated during the process, are all directly related to current. For this reason, best results will be achieved through use of an adjustable, constant-current power supply. A 12V or 15V wall wart can be used, but results are likely to be inconsistent. If this is the only option available for your work, I suggest connecting a DVM between the wall wart and the part being anodized so that current can be monitored.

Jack

6/25/2019 08:58:27 am

Does anyone know of a source for a few titanium spring clips at a reasonable price? I've been using aluminum machine screws and aluminum wire, but some of the pieces I want to make can't be attached this way.

brett G

7/8/2019 12:55:05 am

Back again with another issue.
using the 720 rules and running my power supply in CC mode.

I can achieve the required amps for surface area yet my volts are still on the high side which maybe causing burn.

so using the caswell LCD method and running at 4.5 amp/FT2 for 20minutes
say it states peak voltage 11 yet its running at 19
I know people say just let the volts do what they want and concentrate on the amps being right.

Checked my solution ph 1-2 and i aimed for 25% Sodium Bisulfate

its suggested that the concentration could be a issue causing the volts to increase.

Anyone else having similar problems with voltage .

also some white rings on my latest run
https://forum.caswellplating.com/forum/anodizing-questions/143873-surface-issues

thanks

Jack

7/8/2019 08:37:59 am

I wouldn't worry about voltage in this range, although it does provide a rough indication of the condition of the bath. Generally speaking, only excessive current can burn a part during anodizing.

It's odd you would have the same pattern on multiple parts. A few things come to mind. First, distilled water should be used for sealing.The parts should be fully submerged at all times. Is there anything unusual regarding the shape or position of the electrodes in the bath?

My earlier comments regarding multiple pieces might apply here. Is the wire shown in the photos titanium? Any chance some of the parts might not be making good electrical contact during the process? If the electrical connection to a part fails, the CC power supply will increase voltage in order to maintain the current, and the current not consumed by that part will then be directed to the other parts in the bath. As an example, let's say there are 10 parts in the bath, and you calculate the necessary current to be 4 amps. If half those parts fail to make contact with the wire, the CC supply will still put out 4 amps, but now the remaining parts will each see twice the current you intended. That might cause burning or other odd effects.

Bear in mind, I'm just throwing out ideas here. It's difficult to diagnose a failure like this remotely.

Brett G

7/8/2019 01:55:36 pm

Hi Jack thanks for the support.
Yes I’m using distilled water in all of my processes.
Including sealing.
The electrodes are in the centre with a cathode either side around 5” away both sides so even.
Ye Ti wire shown in images and connection wise I understand but they
Are all the same I assume when I’m connecting the wire with a spring fit in the hole as usually if too loose part with move or fall off the wire.

I will look into your previous posts on multiple parts but yes I understand your logic
I’m unsure why they are uniformed in patterns which is strange

Jack

7/12/2019 12:44:09 pm

Well, I just ran into a problem I hadn't seen before. I milled an aluminum plate yesterday and wanted to give it a quick anodizing to protect it during use. Nothing fancy, just a clear coat that I'll seal with boiling water. After setting everything up, I turned up the current limiter, but hardly any output voltage was registering (less than 0.5V at 1.25A). It's a homemade limiter, so thinking some component must have failed, I tested the output with my meter to confirm what I was seeing. That didn't reveal any issues, so as a sanity check, I applied two C-cells in series to the bath. Wow, with 3V, the tank drew nearly 3A from the batteries!

I finally realized the problem was being caused by the fact the plate wasn't parallel to the electrodes in the tank. It was angled on the single wire supporting it at about 45 degrees. Apparently, the overall resistance of the tank is determined in large part by the distance of the part to the electrodes, even if only the edges of the part are near the electrodes. After I straightened up the plate, initial voltage across the tank rose to roughly 8V.

I've always assumed that the current flow through the tank is dispersed by the acid bath. This would mean positioning of the part isn't overly critical. That's clearly not true. If I had continued with the process without straightening the plate, I have to assume the edges near the electrodes would have been deeply anodized, with only a thin layer applied to the rest of it. Likewise, I think this means that a large flat part hung vertically in the bath needs to be reasonably centered between the electrodes. Otherwise, the two sides won't anodize to the same depth.

Maybe this is common sense to everyone else, but it got me. Hopefully my experience will be helpful to others in the future.

brettG

8/8/2019 01:34:24 pm

Hi , so a follow on from my previous issues .
Seemed to eliminate the problem with white markings .
Secondly the surface finish is more uniformed yet it has a faded finish where it seems the dye uptake is a issue.

Tried running in both cv @15v and cc @720 mode , the latter being the better of the 2 yet still not the best finish.

Acid condition 25% concentration - 70f - 90minutes @ 6amp/sf
Dye - 15min - 140f
Seal - low temp 30c for 20min - 24hr hang dry.

Some results of both CV & CC mode https://imgur.com/a/1uvRPLZ

Thanks for looking

Jack

8/8/2019 07:26:51 pm

Brett, you might be entering an area of the process that I'm not qualified to advise you about. All my anodizing is clear, not dyed. Still, the ability of the piece to take dye is dependent on the anodizing process itself being correct.

With that in mind, let me ask you something about the two methods you used. When you were in CV mode at 15V, how much current was being drawn, say, half way into the process? Was it roughly 6A/sf, or was the value way off? Similarly, when you were using CC at 6A/sf, what was the approximate voltage, half way through the process?

Is 25% the recommended strength? I'm using sulfuric acid, but at higher concentrations.

BrettG

8/8/2019 10:36:14 pm

First off , thanks once again Jack for taking the time to respond and help me.
In CV mode with a surface area of 20sq inches , amps = 0.46
In CC mode with a surface area of 40sq inches , volts = 22.4 @ 6sq ft

The volts seemed to be on the higher end in CC mode when using the 720 formula it suggest peak volts 15 yet they are 22.4

Both ran for 90minutes under the same 70f temp / agitation conditions.

Concentration in the OP suggests 20% but can be ran upto 30%
So I aimed for the middle 25% to account for movement either way incase of evaporation / dilution.
I have ran under the same conditions with dye ph around 6 on my red dye with the same washed out results .
Used both Ti wire and aluminium wire.
I have had good results in the past so I know I’m doing something write yet it’s a bit hit or miss over the previous runs even though I run the same on each stage of the process.
So just trying to get it sorted once and for all.
My acid I’m now thinking of replacing but over its time hasn’t done much anodising in it so I assume the dissolved aluminium levels not to be high.

Thanks once again and sorry about the wall of text

Jack

8/10/2019 02:09:47 pm

Brett, CC is always the method you should use. There is no benefit to be derived from CV operation, and there's a risk parts will be burned or electrical contact broken due to the heavy current draw that can result at startup. Yes, 22.4 volts seems high. I think this implies the solution is too weak, but that might not be the issue. If the CV supply was able to maintain the current you set for the duration of the cycle, the process should have completed satisfactorily. Rod's comment about the dye temperature might be correct, and I should probably bow out at this point. I just don't have enough experience with dyeing to advise you further. Good luck with everything!

Rod

8/10/2019 10:18:50 am

If I remember correctly the dye process is supposed to be at approx 100 deg F not 140.
I think you are actually sealing the parts at the 140 temp and may be the problem with it not taking well.

brettG

8/16/2019 11:42:09 pm

Thanks for the response Rod but going off most sites and searches all suggest 140f to be the temp required in the Dye bath, including the notes that came with the Dye when purchased.

I know you can go lower with temps and even cold with some coloured dyes but I know black ( testing colour ) requires 140f.

John

8/18/2019 07:37:36 am

I go waaay beyond 140 and more like 180. I also see that for my purposes RIT does a better job than the Caswell's stuff, so when I saw that the Caswell's stuff for some reason or another didn't blacken my stuff I added a packet of RIT. Maybe I got things going so that my grain size is too big for the Caswell's dye to have any capillary effect? I use as high an ASF as I can get away with without disintegrating my hanging wire. Utilizing ice packs too.

ManMaths

8/22/2019 12:29:32 am

Possible to help me out on my maths please.

So going off previous advice above.
to achieve a 30% concentration for 25 Ltrs of solution.

I would need

17500 ml – 17.5 ltrs water
7500g – 7.5 kg SB Acid
= 25 Ltrs @ 30%

700ml Water + 300g SB = 1 Ltr Solution.

Jeff Thompson

11/23/2019 07:20:28 am

I tend not to promote things, but I came across a black dye and it is the best I have ever seen. It will even dye your parts cold. 100 degrees to 140 degrees. They only offer Blue and Black at this time. So I thought I would pass it on. https://www.poomadyes.com/

chananiel P Wizman

12/18/2019 03:59:21 pm

TSP for degreasing. Is this what you add to the water and then boil it to 130F for degreasing. I just bought something called SP from an outfit on then some website claims its just TSP which sells for like 1/3 the price. Confused.

Jack

12/19/2019 05:22:39 am

TSP is a toxic chemical that can act as a hard core cleaner to remove stains, mildew, old paint, and many other blemishes. However, none of that should be present after the aluminum is worked and ready for anodizing. In my case, the pieces are either sanded or buffed after machining, so the only issue I need to deal with is oil. Even then, I wash or wipe the work with mineral spirits as part of the prep. The little oil that's left is easily removed with dishwashing liquid. In the rare instance where that's not sufficient, as evidenced by a water bead test, I follow up with a spray cleaner from the local hardware store. The latter probably contains a certain amount of TSP, but it's very dilute and not nearly as "unfriendly" as the powder or concentrate. I have yet to have an anodizing job fail due to poor cleaning.

Tyson

12/28/2019 12:20:48 am

Would this work on aluminum gaming dice?

Ken

12/28/2019 05:26:33 pm

Tyson,
Sure, just clean well and if it is standard aluminum it should work just fine, Ken.

Bill

1/12/2020 02:33:25 pm

Hi Ken and all on the blog from over the pond, what a great depository of information this is.

I've wanted to clear anodise some items I'm making for a motorbike project for a while, came across this blog and decided to give it a go tonight, as a simple first try I used battery acid out of an old dead battery, it was a bit murky but worked.

My test piece was a section of anodised aluminium rod, my process and results as follows.

Drilled a 4mm hole in the top of the rod for connection and suspension, stripped the old coating off for two thirds of the length using caustic soda

I then marked out 4 test sections as follows, 1) left matt as it came out of the soda, 2) polished to high shine with Solvol, 3) a satin grained finish running length ways, 4) a satin grained finish around the circumference ( both done with 200 wet and dry ).

Used a plastic container, and a lead cathode, for a power supply I used a fully charged 12 car battery connected to an old style battery charger.

Used traffic film remover as an initial clean, washed off with tap water, then wiped down with panel wipe to ensure there were no greasy, oily residues.

To make the hanger I cut a 4mm strip off a piece of 1.5mm ally scrap I had to hand, bent this into an S shape, pushed one end through the hole and nipped it up with a pair of pliers.

The other end of the S was hooked over the edge of the container with the + clamp attached, the top of the lead ( previously cleaned as above ) was bent over, hooked over the edge of the container and the - clamp attached, switched it all on, cooked and ate my tea and 1.5 hours later had the nice surprise that it had worked.

Rinsed and boiled it, the 4 finishes look OK and I was surprised that the muddy acid hadn't caused any problems or discolouration.

One thing I did notice though was that the lead had taken on a slight bronze hue ?

Not so bad for a rapidly cobbled up, Heath Robinson, jury rig. 😉

I'll be making a proper setup during the week using bisulfate, what's the betting I won't get as good a finish first time doing it the proper way !

Could I just ask 1 question, all my other queries have been answered it the blog.

The question is, at the boiling stage, if this was done in a pressure cooker, would this allow for a shorter sealing stage, due to the higher water temperature ?

Cheers, Bill

Ken

1/13/2020 10:18:45 am

Bill,
Not really as the act of sealing the pores with the dye is a process that requires a little time, not higher temperature. There are other sealers but water is cheap and works well. Ken.

Jools

1/18/2020 12:27:08 pm

Hi Ken

Excellent tutorial!

I have one question which is: Is there any difference between the hardness of a part anodised this way to a part anodised in Sulphuric acid? Are they as wear and scratch resistant?

Cheers

Jools

Ken

2/3/2020 08:30:10 am

Jools,
There is no difference, Ken.

Brett G

2/26/2020 12:51:08 am

Can anyone help please.
Ive been doing this techinque with some success over a few years.

Come to replace my Sb acid solution currently 20% to a new stronger mix of 30% in Di water.

Diluted fine in warm water as it should, when cooled and left in room temp conditions (winter in the uk ) it recrystalized (25 ltr tank ) not all of it.

So what next , would I be able to heat it back up and then remove 5ltrs of the solution and replace with just standard Di water to dilute the mixture so it dosent crystalize in future ?

If I heat it up to the required temp of 68f before a run it still has crystals so solution is no good.

Phillip

4/25/2020 01:32:43 pm

I had good success with this on an AR-15 lower on my third attempt. I used a car battery charger at 12v, which gave me around 3 amps. This took around 3 hours to do it, but it took the dye beautifully when I was done. Previous efforts would not hold dye, but once I looked up the "rule of 720" and got the time right, the results were great.

Rex Frost

6/7/2020 12:43:23 pm

Does the part have to be dyed after anodizing? I was thinking the anodize give a hard coat the paint with cerakote ?

Ken

6/7/2020 03:52:31 pm

Rex,
No but do seal in the hot water to seal the micro pores created during anodizing. Also, aluminum already has a protective layer of oxide so anodizing may no be necessary, Ken.

Rodrigo

7/8/2020 08:51:50 pm

Hi! I’m preparing for some Al. 6061 anodizing by your instructions. I have a couple of doubts:

I’ll need to anodize in Opaque Black some really thin and small parts (hollow 12mm length cylinders with 16mm diameter and 1 mm wall thickness. Why is black the most difficult color to dye? Are there any special instructions for anodizing in black?

Second: does anodizing makes the part thinner, or thicker? Does the dye layer increase the thickness of the part? If so, how much? Does the caustic soda solution makes the part thinner? Does the SB 20% solution also wears the surface of the part, decreasing it’s thickness?

Thanks!

Jack

7/16/2020 02:36:46 pm

You've probably got the answers you needed by now, but I'll do what I can. Unfortunately, I only do clear anodizing, so I have no experience with dyeing. Anodizing does slightly increase the thickness of the part. Caustic soda (lye), which I no longer use, removes material, making the part thinner. There are a lot of variables in both processes, including temperature. If this is a critical aspect of your work, I would say you need to do a trial run under controlled conditions and make measurements. Don't risk a large quantity of work.

Rodrigo Bordin

7/22/2020 02:19:19 pm

Thanks Jack! I'm starting my tests. I'm getting a weird thing about the voltage/current.

I set up firts the Caustic Soda, and it worked. with the part submerged for 3 minutes the difference in diameters of the part were negligible.

Then I prepared the acid solution at 20%, I used a 10 cm aluminum tube as cathode, used a 2mm thick aluminum wire to connect the positive pole of the supply to my piece (which is really small (1.5mm thick 10mm long tube). I let my small tube completely submerged.

I set my bench supply to 20V and 1A max, and the weird thing is that it draws only 10 to 15mA. I tried changing the thickness of the aluminum wire that connects the anode to the part, to a really thin one, and nothing changed. I can't make it draw more current than this. I can see bubbles being formed in the cathode. And some tiny tiny ones over my piece and over the aluminum wire connecting my piece to the anode.

Is this normal?

LarryW

7/16/2020 02:29:39 am

hey guys-- I'm playing around with the 720 calculator. Not sure exactly what value to use for the Current Density field. How do I determine an appropriate number?

Thanks for the help!

Jack

7/16/2020 02:29:44 pm

The link below contains an active version of the calculator. The instructions underneath the calculator include a rudimentary notation:

"The LCD process is designed for current densities between 3 and 6 amps/ft². The 1:3 acid ratio has been successfully pushed to 12 amps/ft² with aggressive agitation and careful temperature control."

In my experience, there's no significant difference between 3A and 6A current density, per se. When I'm setting it up, I try to do a rough analysis based on two factors.

First, there's time. if the time is extremely short because the piece is small, I reduce the density. Anything less then 20-30 minutes probably increases the inaccuracies of the process. For example, if the calculator determines only 5 minutes is required, a 1 minute deviation is 20%. Extending the total time to 30 minutes, the error becomes much smaller. Time can also be too long. I wouldn't want to wait two hours for a piece that can be done in one hour.

Second, I try to be aware of the issue of bath heating, especially in the summer (my system is in the garage). The calculator assumes the user has a constant current source for powering the electrodes. This means the voltage will start at a fairly low value, then rise as the piece being anodized acquires resistance from the developing oxide coating. Total power dissipation into the bath will be highest near the end of the process.

For example, let's say you anodize a sheet of aluminum 12" square. That's 144 sq inches. If current density is set to 6A, peak voltage will be 15V. That's 90W of power being dissipated by the bath near the end of the cycle. OTOH, setting the current density to 3A, peak voltage will be 7.5V. That's only 22.5W. Even though process time will be longer, the bath will probably be better able to dissipate this reduced level of heat.

Hope this is helpful.

http://www.ndhsubmersiblescience.com/ano/720rule.html

LarryW

7/16/2020 05:55:17 pm

hey Jack--

thanks a bunch for the reply about density, very helpful indeed. and for the link to the calculator. i can see how a guy can get way smarter by hanging here. all you guys are the best.

soooooo, on a very pragmatic level looks like i can use the density field is an "adjustment" number - the calculator takes whatever value i put there and backs out the values for the other fields to keep everything in sync. that allows me to massage the last 3 numbers into something i can most easily apply at the bench. long as i stay within the stated range i can get those bottom fields to dance around into whatever works best for the task. zat so?

clearly i need to step up to a nice bench power supply. i'll be getting one on amzn tonight. while i have your ear i have a couple more questions? i understand about this anodizing stuff being very much an art. granted that the number of variables is large, i'm still hoping for your educated opinion about a couple things. here's the deal: i get 3" aluminum plugs that are residue in a stamping process from 12 ga 5086 sheet. i get them by the boatload then sell'em 10 to 100 a time on ebay, etc. it's incredible what creative folks are able to figure out what to do with them. amazing, really. because i buy them at scrap i can resell them way cheaper than folks expect to pay, which is great, but i still need to greatly expand the market. one of the things being considered is to anodize them with lots of pretty colors for the craft people. thanks mostly to ken's great website here i have enough confidence now to tackle the technical issues, but i haven't been doing it long enough to get a feel for profit margin. for the craft mkt i gotta keep the price really low. i'm really hitting a wall trying to get google to get me a price for anodizing services. is there any sort of industry guideline, say price per sq in or something, that'll give me a ballpark number for production costs? i know it's just a wild guess because of so many variables, but i need something better than "well, it sorts depends..." what kind of cost per unit should i aim for on doing a 3" disc, say a dozen or so at a time, with a DIY homebrew setup, paying mostly retail for supplies, etc? if you guys with lots of experience had a small setup like this, what kind of number would you target for unit cost?

what kind of rejection rate do you think is reasonable? if i can get production numbers up enough to justify dedicated ventilation, etc. should i be motivated to move to sulfuric acid? why or why not?

thank you VERY much for your time and thoughts--

--larryW

Jack

7/23/2020 11:33:28 am

Larry, I can't help at all regarding the cost of commercial anodizing. I'm just a hobbyist with a mill and a small anodizing tank. You should look for a company that does metal finishing, and maybe take or mail them a sample. I only do clear anodizing, no colors, and I've never paid to have this done. Good luck with everything!

larryW

7/23/2020 05:50:29 pm

hey Jack--

thank you for the reply. i took your advice and talked to a couple of local commercial outfits. it was certainly informative.

but seems the guys who are pros and do commercial quantities have their system down to more a science than an art, for obvious reasons. they didn't care much about even talking about trying crazy color ideas that artists might want to try.

even though you don't have to worry about sealing in any dyes i assume your clear process still goes through a sealing step - zat so?

one of the things i wanted to talk about with the pros was getting a commercial-size batch of discs done in their big anodizing vats and then bring them back home to color and seal. or maybe even send them to customers in a plastic bag and let them do the coloring. i've seen beautiful pieces that seemed to blend colors by having the dye fade from one color into another, i assume by dipping different sides into a bath and feathering the depth of the dip. also, some of the guys who hang out here say they have success with things like RIT dye, and can take advantage of an awesome palate of mixed colors. the shop guys just scoffed whenever i mentioned something like a fabric dye - apparently a truly amateur question:) common wisdom from them was that there was a limited time window between the anodizing bath and the dye/seal baths but nobody seemed to know how large the window was, and if it was measured in minutes or days. any thoughts?

i apologize about peppering you with all these coloring questions right after you just told me you don't mess with dyes. i guess i'm hoping some of the folks who monitor all the entries might jump in with some thoughts...

many thanks to you for indulging newbies like me with all these dumb questions;)

--larryW

Jack

7/25/2020 11:32:47 pm

If I needed to color my work, I would obtain the dye from Caswell. Knowing the dye is commercial quality and having access to their customer service would eliminate one big variable in learning and perfecting the process. Yes, I do seal the clear pieces using boiling distilled water (no other chemicals). It's not clear to me whether the use of an actual "sealer" would be beneficial, but this has worked well. I usually apply a brushed or swirled finish on the work before anodizing, and the resulting appearance is very professional.

Rodrigo

7/25/2020 08:00:44 am

Hi! I've been testing my anodizing setup. But I have some doubts...

Are there degrees of anodization in a piece of aluminum? Can you over-anodize a piece? Anodize too much? Or when the current decreases until almost nothing it's surely done and anodized?

If you anodize a piece of aluminum and while inside the anodizing solution, you move the hook (to expose that hook part that was in touch with the piecet), will it continue to anodize that "previously unexposed part" until it gets anodized as much as the one already anodized?

If the dye doesn't attach with much intensity, or it doesn't get saturated, opaque, in the anodized piece, the cause could be that the part was not anodized properly?

Or not pre-etched in soda enough beforehand, to create greater pores?

Or if the part was anodized (checked with the multimeter) it should always retain the color, and problem is solely in the type of dye?

Thanks for the help!

Jeff Thompson

8/5/2020 12:11:38 pm

Stainless steel. Has anyone used it for the anode? I have been using titanium. I just have a lot of stainless laying around the shop.

Jack

8/6/2020 11:01:45 pm

I think you meant to ask about the cathode (the anode is the workpiece). Alloys containing iron aren't suitable for this.

Jeff Thompson

8/7/2020 05:31:16 am

I am talking about the item used to connect the part to be andozided to the rail that has the positive terminal. I use titanium rods to connect my parts to the rail, so I can submerge them into the solution. That would be the Anode correct? So iron containing items cannot be used at all?

Jack

8/7/2020 09:18:43 am

Jeff, if anything containing iron is submerged in the tank, it will contaminate the bath. I use bare aluminum wire for this. It's less costly than titanium, but it has to be discarded after each use because it becomes anodized.

Jeff Thompson

8/10/2020 06:13:22 am

Thank you for the information.

Andrew

10/11/2020 06:05:48 am

Hey Ken,
What's the logic behind the ~20 wt% sodium bisulphate?

I would have thought you'd want to keep the amount of H+ the same as standard anodisation, but that works out at about double the concentration you use. Did you guess and found it worked ok, or is there some reasoning?

Ken

10/12/2020 10:09:47 am

Andrew,
I did a ladder study due to the variable nature of H+ in commercial product. 20% was the best and most repeatable and was based on logic. Thanks, Ken.

Allen

10/15/2020 07:07:49 pm

Thank you very much for your in-depth how to on anodizing.

I have been interested in the process since my teenage years and have now just completed my first parts with amazing results.

Mohsin Khan link

10/25/2020 11:25:02 pm

Looking to get a car charger that is capable of fast charging the pixel 3 xl. Wondered what you guys have used, and what you’d recommend? And what’s the best wireless charging pad for the quickest charge? Aside from the pixel stand

Nora Black link

12/27/2020 03:19:36 pm

This is a great posst

Jack

1/6/2021 03:56:27 pm

Ken, I'm anodizing some work that's larger than in the past. One item is a long panel that won't fit in the pan I normally use to boil and seal my work. This is all clear anodized, so I'm not worried about sealing in color. Also, this item is for indoor use, but it will be subjected to frequent handling (front panel for an electronics item). In your opinion, will there be a problem if I omit the boiling step? Will it be more susceptible to staining or other issues if it's not sealed? Thanks!

Ken

1/8/2021 09:03:38 am

Jack,
The anodized surface needs to be boiled to seal the micro pits and provide surface resistance. Ken.

Jack

1/8/2021 11:13:16 am

OK, maybe the local restaurant supply has a stainless pan large enough for this. Thanks!

Patty link

1/20/2021 08:43:19 am

Thanks for the info Ken-
Worked !

A couple of things I learned that I hadn't read that I found important. First NEVER touch the part your anodizing ,once you start the process, even with gloves, or a stirring stick or tweezers.Keep the part hanging through the process of anodizing, dying & sealing.
Don't let it touch the bottom.

Rit Dye - Dark Green with double concentration then you quoted looks mighty black to me .

I'm pretty encouraged with the process- first time out & I have parts that look pretty good.
Thank you,
Patty

Ken

1/20/2021 10:19:21 am

Patty,
Sounds promising. I have been experimenting with heavy duty aluminum foil as a possible art form. Will post when I complete the project. Thanks, Ken.

Jack

1/20/2021 11:00:04 am

That's very interesting. I never even thought about anodizing aluminum foil. Does it become stiff after being anodized? I'd like to see your results if you take pics.

Ken

1/20/2021 03:07:51 pm

Jack,
No the foil remains unchanged but take color in strange and interesting ways and looks worthwhile pursuing. Will post as I get something for readers. Thanks Jack, Ken.

Ricardo

1/27/2021 10:46:54 am

First, thanks for all useful information.

I want to share my experience trying hard anodizing a fry pan.
The attempt was to hard anodize a frying pan with NaHSO4 solution at about 1º-4º C, using the freezing cold weather that was two weeks ago, and the snow accumulated outside.
The piece to anodize was a 28 cm diameter cast aluminum fry pan which had partially lost its anti adherent layer. I sanded the inner surface to remove all the anti stick coating layers (coarse and medium grinding, not polished). After that, the bare aluminum surface was washed and then etched with 2% NaOH solution.
I used a plastic thick foil around the outside of the pan to make a cylindrical container with the pan as the bottom and filled with 20% NaHSO4 solution; the solution level was 2 cm above the pan top.
Then I put it inside a bigger container with some snow and left them outside to get chilled. When the solution was about 1º-4ª C, it was connected an unregulated DC power supply (not made for this job; 230V/30V AC transformer 225VA, full wave rectifier, 18800uF in smoothing caps) : positive to pan, negative to an aluminun electrode (old car plate rolled and sumerged vertically without touching the pan).
Initially the current was about 8A at 28V, but very fast it settled about 5A and 32V aprox and after some minutes it stabilized at 3.4A 38V-40V. Every 15 minutes or when the current appeared to rise, added some snow to the bigger container in order to lower the pan temp, but I didn't check the temp.
After 70 minutes I removed the solution and rinsed the pan with fresh tap water. The color of the anodized surface was very dark grey, and it was very hard, not easily scratched with a steel knive egde. So I think it was type III anodized.

By the way, the resulting surface is not at all non-sticking, but it resists very well the heat and the washing.
Best regards,
Ricardo

Ken

1/27/2021 03:34:06 pm

Ricardo,
Congratulations as this is the first post for hard anodizing. The documentation was excellent and your time is well appreciated. Thanks for the comment and hard work! Ken.

Patty link

3/3/2021 06:20:52 am

Ken,
I have a question-
So I anodized a pair of earrings last night (6061 AL), following the Caswell 720 cal.
First cleaning them in a metal degreaser, followed by dawn.
I went for a 1 mil long anodize, as I've seen better results with that (2 hours).
After anodizing,I dunked them in a baking soda + RO water , followed by a RO H20 rinse.
So I dyed them ( powered rit dye +RO H20), and in fact left them hang in the dye all night.

So this morning when I took them out of the dye they were indeed quite uniformly dark purple, HOWEVER after I hung them in the boiling water for 30 minutes they came out spotty- looking almost like a glitter pattern on them.

Any idea why ??
Thanks, Patty

PS- Meant to tell you a couple of weeks ago, that YOU were quoted in " Home Shop Machinist" Magazine for your anodizing - famous you are :-)

PaulK

3/13/2021 06:56:23 am

Hi everyone, a first-time poster here. Here are some notes/questions from my first few attempts, results are fairly good so far.

1) RIT liquid dye comes in a 8 oz bottle (for the $3 all-purpose dyes) or 7 oz for the $4.50 synthetic type at Walmart. I just dump the whole bottle into a 1/2 gallon bottle and use that strength; dye time can be adjusted to get the saturation you want. I don't think there are any drawbacks to using it that concentrated. Has anyone determined if all-purpose or synthetic dye is better for any reason?

2) The RIT black turned out a lovely bronze, but does the Dylon black work better? If so which one, and liquid or power type?

3) I had decent results with just tap water all around, is distilled or filtered water really that much better? I did buy an $10 aquarium air pump and used it to agitate the bath, on the idea that it will help spread out any contaminates or uneven plating.

4) How dangerous are the anodizing fumes? Is it just hydrogen? Assuming its not concentrated enough to cause a fire/explosion hazard, how much ventilation is enough (eg dilution using fans versus directly capturing it to the outside)?

5) What is a good cheap polishing material? I tried Comet cleaner, but Harbor Freight $5 polishing compound sticks seem better. What about liquid types, many seem pricey.

6) One tip, I found you need to adjust the voltage to get the current recommended by the 720 rule. Changing the bath concentration does not help much. After the first minute the current stays about the same so you don't "really" need a fancy constant-current supply. A good supply range is 10 to 20 volts, up to 5 amps. But a used desktop PC supply also works on the fixed 5 or 12V output if you don't need this level of control.

7) Anodizing time is 1 to 2 hours, for a normal plating thickness and pore size (for good dye uptake), and fixed current per square inch. In other words, you can't really shorten the time much, its simply a matter of how the aluminum does its thing. I have not experimented with times for 5052 sheet metal versus 6061 machined parts yet.

Thanks for the great posts everyone, so glad not having to mess with sulfuric acid!

-Paul

Jack

11/2/2021 04:02:51 pm

So sorry to hear Ken has passed. He was a great guy who always helped when I needed it. Rest in peace.

TNN Engineering link

11/2/2021 11:34:04 pm

Very informative ideas that everyone can follow through it. Anodizing is best for aluminum and other steel materials.

Henry Killingsworth link

8/3/2022 12:21:39 pm

It was interesting when you mentioned that anodizing shouldn't be attempted by people at home. If you are in need of anodizing, I would think that it would be best to always have an experienced professional handle it for you. Having a professional handle the anodizing seems like the best way to make sure it is done safely.

Jack

8/4/2022 01:52:57 pm

No one said anodizing shouldn't be attempted at home. I've been doing it with excellent results for years.

Vancouver Anodizing link

2/17/2023 03:29:04 am

The process of anodizing and dying aluminium without the use of battery acid is laid out in great detail in a blog article by observationsblog.com. Instructions on how to accomplish this, together with a list of the necessary equipment and chemicals, are included in the post. This post is quite informative and can be used as a reference when anodizing aluminium without battery acid.

David MacQuarrie

3/24/2023 11:02:26 am

After many months of so-so results with this method, I began using a 15v 2 amp power supply. A world of difference! Getting very professional results and deep colours. Also, I believe warming the dye is also worthwhile.
6v just doesnt seem to be enough

Jack

3/24/2023 12:23:51 pm

6V is definitely not enough. One problem is that the resistance of the work increases as the oxide layer builds. The electrical current will taper off, and as the process moves towards equilibrium, the pores begin to close up. This is another reason why a constant-current supply is so beneficial to the process.

Matt Gazz

6/7/2023 07:56:03 pm

I had some parts professionally Anodised recently in natural colour. If I now want to colour them is it possible to do? If so where/how do I start?
Cheers Matt

Jack

6/7/2023 08:58:09 pm

In order to dye it, the existing anodized surface (aluminum oxide layer) will need to be stripped using a caustic chemical such as sodium hydroxide (lye). Then it will need to be anodized again to produce open pores, dyed and sealed. The only other method I know of to color it is paint. It can't be powder coated because the anodized surface is non-conductive and the uncured powder won't adhere.

Anodizing and dyeing aluminum without battery acid...

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