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Composition of black anodized Al part

I have an aluminum washer with a black finish. The EDS spec shows Al, S, Cr and Ni. Can I assume that it is anodized in a sulfuric acid bath and then sealed in Na dichromate and Ni Acetate. Do the sealing compounds become a part of the anodized surface? Could it be black nickel plating?

Mala Dehra
engineer - Tampa, Florida USA
July 15, 2008

July 15, 2008

Hi, Mala. I think a microscopic cross-sectioning would be far more revealing about what you are looking at.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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