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Corrosion Protection/Plating Suitable for Copper and Aluminum

I currently work in the automotive industry and am looking for some guidance regarding a suitable surface finish that adheres well to both copper and aluminum substrates. We manufacture an electrical terminal that is part copper and part aluminum and we need to prevent corrosion at this junction (incl. galvanic). Typical terminal materials are brasses or coppers and receive as standard a surface finish of 5-8 microns of tin. We were thinking of a Zinc Nickel surface finish, but didn't know if there was something better (performance or cost). We are looking for something in the 700+ hour salt spray range. Two of our key concerns are the adhesion of coating to the aluminum substrate, and also the ductility of the finish as the parts may be bent after plating. Any advice would be greatly appreciated

Rob McClelland
Engineer - Southfield, Michigan
May 20, 2009

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Hi, Rob. I didn't follow if there is anything wrong with the tin plating. The primary reason for the existence of zinc alloy platings like zinc-nickel is for sacrificial protection for steel -- so I'm not sure how appropriate they would be for aluminum and copper surfaces. Tin-zinc would be more flexible and malleable than zinc-nickel. Tin-nickel is a pretty extraordinary surface you might want to consider -- listen to our podcast, "The lost art on nickel-tin plating". Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 21, 2009