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Help solving problems with Tin sol potassium stannate plating bath

We are operating a tinsol potassium stannate tin bath with steel anodes, we are presently experiencing two problems:

1. small blisters which collapse under pressure and
2. black smut in some of the tin deposits

The first may be cleaning but if we were running a conventional bath I would suspect hydrogen peroxide was required, Has anyone had to add this to a tin-sol bath? The bath is 5 years old.

william f. morgan
- saratoga springs, new york
1999

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Your chemical vendor should be able to answer this question. If he can't or will not, consider switching vendors to one that has a good rep that you see more than twice a year and with a good tech service shop that does not put you at the bottom of the list because you are not a "large account".

Have you changed your process cycle in the time frame of the problem starting? I had a problem and lost a potential good account because of tiny blisters that resulted from over cleaning and over etching a hard 4340 set of parts. Of course, we found this out in the lab about a week after the account went away.

James Watts
- Navarre, Florida
1999

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If you're seeing the black smut in the deposit it may be Carbon from the steel anodes you are using. Although Tin star anodes are a little harder to maintain (the film), they are well worth the effort. Not having to replace the Tin as much and not having the smut from the anodes makes up for it.

Jim Conner
Anoplex Software

Mabank, Texas USA

1999