Letter 41055

Powder coating anodized aluminum parts

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I have thousands of small black anodized aluminum parts that I wish to powder coat w/o first stripping. Is there any problem w/ compatibility or significantly diminished adhesion?

Chuck DeWitt
electronics - Hamilton, MT, USA

There is no 100% answer. You can paint over sulfuric anodized parts in most cases. In a few, dye might cause a problem. there are several paints that do not like chromate sealed or chromic acid anodizing. Seal does not make a lot of difference unless the parts are quite old, then sealing helps. Wait a day after anodizing to paint as your powder coat cure temp might cause a lot of water outgassing. I think that unsealed paints better, but I have read several opinions to the contrary. Best is what works for you.

James Watts
- Navarre, Florida

Is it possible or is there a specific process to anodize aluminum pre-bend and drilling without molecular failure and eventual flaking off of the finish?

Thomas Babcock
Bozeman, MT, USA

Hi, Thomas. No, I don't think so. Anodizing is a very hard and brittle aluminum oxide ceramic coating. You can't significantly bend it without it badly cracking. If it's going to be bent, chromate conversion coating sounds like a better choice.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

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