Aluminum Anodizing and Chemical Conversion Coating same part?

Letter 21098

Aluminum Anodizing and Chemical Conversion Coating same part?

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I have a machined aluminum 6061-T651 housing which needs a conductive coating (chromate conversion clear irridite) for electrical purposes but also a hard anodizing to strenghten a few large fine tapped threads. Can I mask the part and perform both operations? I would prefer not to mask the part and perform a single finishing operation to both harden the threads and promote conductivity. Any suggests?

Thanks very much,

Jon Gallant
- Ottawa, Ontario, Canada

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Hard anodizing will not strengthen threads. It will increase the wear resistance. That said, hard anodizing would not rank high on my list for threads since there is a rotational crushing effect that I think will cause the hard coat to not last well. If this is internal threads, why not heli-coils? If it is external, why not electroless nickel? But, in answer to your question, you are going to have to mask at least once. Typical is to chromate, mask and then anodize. The exact procedure will depend on the shop and the part. There is no 100% answer.

James Watts
- Navarre, Florida

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