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Black anodize is flaking

We have been black anodizing parts for years. Have recently run into the problem of the black dye flaking off. The parts are anodized, dyed, then sealed in a nickel acetate solution. the parts then go on for further processing which requires a 150F 30 min cure for some potting. After the bake if you put a piece of tape on the parts it will pull the black off. we lengthened the seal time, and this seemed to fix the problem but now we are having the problem again. Any help would be greatly appreciated.

Thank you,

Steve Kingsley
Lab tech - Urbana, Ohio
2003

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Assuming you mean conventional Type II and not some exaggerated definition of "hard coat", dye does not "flake". Anodizing applied over less than completely deoxidized aluminum will chip off and bring the dye with it. Rather yet, you probably revealed the problem when you admitted that increasing the seal time helped. Now go back and make up a new seal, with deI water, with a reputable proprietary nickel acetate seal.

You see, if the dye "wipes off" rather than "flakes off" then for sure sealing is THE problem. So crack down on the seal and the care thereof.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003