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Dry film lubricant not removing prior to anodizing

2007

gentlemen:
I am facing a problem on a new project. The alloy is 6061 aluminum with some dry film lubricant on it from forming operations ( I believe it is graphite based).
Upon anodizing the parts come out with lots of powder.
Two things help: 1. If I go and etch upto 15 minutes, I see very little powder but my dimensions are off and it is not productive for us.
2. No etch helps, but the parts look little off. Not good cosmetically.

Does anyone know about any chemical during soak/etch or desmut which can clean up this dry film lubricant so that I can successfully anodize the parts and do not get any powdery film.
I need 0.4 mil thickness and it is a type 2, green color parts.
Thanks for sharing your input

Hemant Kumar
- Florida, USA

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January 12, 2008

I have seen this problem in extrusions, One solution is to use a solvent based cleaner, (glycol ether, TCE (eesh)) to remove the dry film lubricant.

Most soak cleaners will break down the lubricants over time, and coupled with a good Deoxidizer (should break down the organics that hold the lubricant together chemically) the part will come clean.

First make sure your soak and deox are well within range and are not contaminated


My suggestion:

1. Soak clean at an elevated tempurature (follow your tech data sheet for this one, too high you may etch the part)

2. after rinsing deox the part for an extended period of time (maybe a bit higher on temperature will help here as well, again Tech data sheets help!)

3. After rinsing return the part to the soak cleaner.

4. Rinse and look for waterbreaks.

5. Deox again (may be a bit of overkill,) or etch at this point.

Anodize...

If this does not work, and the glycol ether does not as well, mechanically removing the dry film will be the only option, The good news is that if you

1. remove the excess oils
2. Oxidize the organic binders in the dry film molecule chain
3. Emulsify the lubricants that were held together by the organic binders

you should not have a problem.


Unless the dry film is PTFE based in that case a higher concentration Nitric acid ( 50%) will be needed to attack the binders that hold Teflon together.

lol.. Thats alot to soak up but it works for us.

Ryan Cook
Toccoa, Georgia

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January 22, 2008

Ryan,

I have had practically tried all the options, what you discussed.

Here is what worked for me:
I sent out the white powder after the anodizing for lab testing and found out that it was sort of fluoride based polymer.
You are quite right by thinking it to be PTFE or it could be similar.

I tried to soak the parts in existing deoxidizer which I heated to 150F for 5 minutes.
I could literally see that the dirt on top of part getting dissolved off in a glass beaker experiment.

After that I followed my regular anodizing process, parts came out with no powder.

Another thing which also succeeded was anodizing the parts with No etch. Again parts came out with no powder but the finish is lighter and little uneven color. I guess etch was evening out the base metal.

Thanks

Hemant Kumar
- Florida, USA