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topic 9742

Smutting of Tin on Copper Plated Aluminum


I am barrel plating tin on copper plated aluminum. I have a problem of yellowish spots on the tin plate that later turns grey. I have a cascading final water rinse. The rinse is city water that is 8 grain hardness. I am a novice, so I would like someone to explain the proper steps from the raw aluminum to the copper to the tin to the final rinse. Is a corrosion inhibitor needed, and if so, what kind?

James C. Young
- Cincinnati, Ohio, USA


Are you plating bright acid tin? If so, you may be having a problem with the organics from the brightener. After the tin bath, you might try rinsing followed by a real mild alkaline rinse (or something like Lea Ronal's Neutra Rinse), then another cold rinse followed by a hot final rinse.

Phil Pace
- Tulsa, Oklahoma

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