We are having problems with a yellow stain on some of our tin plated parts. The plating process consists of an initial copper deposit followed by a tin deposit and alkaline rinse. Do you have any suggestions on how to eliminate or at least minimize this problem? S.T.
Answer:
Here are a few things that can cause the staining you are observing.
Copper is present in your stannous tin plating bath. Look at the rinsing process between the copper and tin plating baths.
The alkaline rinse is no longer able to neutralize the dragout from the stannous tin solution. Check the alkalinity of the rinse.
The final rinse is contaminated with dragged-in material from the alkaline rinse. Look at the rinsing steps after the alkaline rinse.
If you need more help with the troubleshooting of this problem get yourself a copy of the book, Trouble in Your Tank, 3rd Edition, by Lawrence J. Durney, which is published by Products Finishing's owner Gardner Publications, 888-527-8803.
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