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Dull spots on bright tin plated copper

Q. We have acid tin brightener bath we found dulls spot on copper pieces after one month storage turn dark spot

ehab ahmed abd alla
sweedy - cairo . egypt
2002

A. I would say that spots are caused by lack of a neutralizing rinse, you can use caustic soda [affil links] on a second rinse after the tin plating, make sure to keep your pH at 10, and after it have a hot rinse prior to the dryer.

Carlos Rodriguez
- Juarez, Chihuahua, Mexico
May 16, 2008

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