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Tin Fluoborate plating bath info

Regarding tinplate manufacture, I have a couple of questions:

1. With the stannous fluoborate bath, is it acidified to prevent hydrolysis to SN(OH)BF4? Is sulfuric acid used for this purpose?

2. What is the E0 value for the reduction reaction involving BF4- ions?

I am a school student (Year 12) and have not been able to find this information anywhere, so I would be really happy if you could help.

PLEASE HELP ME! I know it's your free time too, but I'm really desperate, my local library is no help, and I have only had one opportunity to go to a university library. I can't get there again, and this is the only place on the internet where I could find this topic besides companies' websites, which are in general useless to students. So please reply as soon as possible - the time zone difference delays not only you reading this message, but also me receiving any replies. THANKS VERY VERY MUCH.

Catherine Forrester
- Australia
1999

Fluoboric acid is the acid used. It is added according to titration and the manufacturers specifications. Tin can be plated from a sulphate solution as well (no fluoborate, is cheaper and is functional. The fluoborate bath offers a few properties that some people prefer over the sulphate bath. I have no idea what the Eo is. I believe it will vary slightly with the pH.

James Watts
- Navarre, Florida
1999

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The Eo for the tin in the +2 valence state (at one N) is -0.136; I'm not sure is this answers your inquiry though.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
1999

What is a common range of thicknesses for the tin layer plated? Is 0.00034 mm possible? I may have made a huge error in calculating. Have I?

Catherine Forrester
- Australia
1999

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Yes, I think you did, Catherine. This sounds somewhere between 1/10 and 1/100 of the thickness I would have expected.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
1999

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It should be possible to calculate the E(0) value from the value for Sn2+ -> Sn, and the formation constant for the stannous fluoborate complex. I believe that this value can be found in Meites Handbook of Analytical Chemistry [affil link on Amazon], which any good sized library ought to have.

Dave Wichern
Consultant - The Bronx, New York
1999