I don't know if you want this around if you have kids, but MG Chemicals makes "Liquid Tin" -- which plates in 5 minutes. The contents are nasty -- fluoroboric acid and stannous fluoroborate. Allied Electronics sells it, but not that they will ship all chemicals separately and you pay a UPS surcharge for Hazmat. It's expensive at $27 for 17 ounces.
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Tin Plating
2002-03-03 by caveteursus