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Leaching stains in Nickel Plating on Tin/Lead Medals

2007

We Have a customer manufacturing, amongst other things, medals for competitions. The medals are made from tin/lead. We are however having problems with leaching on the rear of the medals only, appearing after Nickel Plating. The leaching is bluish in colour and I suspect it could be acid.

Nickel is the final Plate. We activate the product for 1 minute in a 5% strength acid dip prior to a cyanide copper strike, pyro copper build and into Nickel bath.

We have tried adding in hot and cold water rinses before and after the acid, and a hot and cold water rinse prior to drying them in an oven. We have also tried substituting the Copper strike with a Brass strike.

I would be very grateful for recommendations.

Mike Campbell
Plating Shop Employee - New Zealand

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Seems to me you've tried hot and cold rinsing everywhere but where it now seems to be needed, Mike -- after the cyanide plating :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007