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Plating onto tin substrate

Q. I have started casting small medallions using lead-free solder (over 99.6% Sn). Sometimes I also mix in 20% bismuth to get a better cast. Now I'm interested in plating them with copper, and possibly gold.

Will copper take to tin? Or should I start with nickel or zinc or something, then copper as the final layer? And the same question for gold really.

Mallory Nichols
- Burnley, England
July 6, 2020

A. Hi Mallory. I think you would be able to do such a process, or have it done, but that the tin & copper or tin & gold, will diffuse into each other too readily. I think you'd probably be better off doing nickel plating as a diffusion barrier first before the copper or the gold. Although I've heard of some adhesion issues when plating onto tin, I would expect that medallions would not be soldered, or exposed to high temperatures or stresses, such that in your case adhesion issues will probably not be a significant problem.

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 2020

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