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Tin over S.S.

Hello everybody: I'm currently acid tin plating(rack) thermostats for the home appliance industry products. It is assembled by two base metals, copper and stainless steel. We can not tin plate over s.s. unless we nickel strike first, correct? The part is completely assembled, will the nickel strike affect or damage the copper? How will this nickel strike benefit or damage the part if any? Thank you for any input that you may have.

Alfredo Garza
- Brownsville, Texas
1999

I will not say that it can not be done, but it will not be easy on a routine basis. A lot is going to depend on how much activation and cleaning the SS is going to require. Copper is very reactive and SS is relatively non reactive. To get the SS active enough to strike and not peel or blister while at the same time not ruining the copper part will be a trick. Selection of acid, concentration, time and temperature will be moderately critical. The two metals in direct contact with each other will make one metal anodic and the other cathodic, probably manifesting itself at the tips, leading to pitting of the more anodic one. A woods nickel strike is the most common strike for SS, but a sulfamate one is fairly good and is not quite as aggressive.It operates at a much higher pH so is a lot faster strike. I assume that you have experience with this part and plating. Since you have brought up the question, I assume that the experience is other than wonderful. Good luck.

James Watts
- Navarre, Florida
1999

Dear James: Thank you for your input, I know it will help me a great deal. have a good friday off !

Alfredo F. Garza
- Brownsville, Texas
1999