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Fall of Sn2+ in tin plating bath

I have been running a 550 gallons tin electro refining prototype without filtration system since 22 feb. The Sn2+ content was 20g/l at the beginning. The solution turned from clear, brown, green then milky. The Sn2+ content is 7g/l. Does it has anything to do with the oxidation of Sn2+ to Sn4+ by air? Are tin impure soluble anodes supposed to supply Sn2+ in order to maintain the current?

Brigitte Peck Ki Laou
Research - Canada
2007

Your Sn2+ is being oxidised to Sn4+ by air. Whilst may Sn2+ salts are soluble, there are not so many Sn4+ ones and they often form insoluble SnO2 or Sn(OH)4, which is a dirty milky white colour

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2007

The Sn2+ usually can be oxidized to sn4+, is there any good method or anti-oxidizer to prevent the oxidation of Sn2+ by the air?

Alan Loo Sai Len
- Malaysia
September 29, 2008

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