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Corrosion resistance of tin plate

We are looking at hot dip tin coating on copper for corrosion resistance to oil with a sulfur content and also as a cheaper alternative to using stainless steel in de-ionised water. Your statement regarding tin plate being porous I assume is with regard to electro-plating. Is hot dip tin better?

Peter Geisler
Thermal exchange ltd - Leicester, England
2003

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I do not know how tin will withstand sulfur containing oil at an elevated temperature, but it should be OK at normal temperatures as long as the sulfur level is not too high. As far as tin porosity is concerned, any coating will be porous if it is thin enough. Most tinplate is now made by electrolytic coating and then flow melting it - this gives a very thin layer of tin on top of an even thinner layer of alloy (in the case of steel, the alloy is FeSn2). In the case of hot dipping, the tin layer is much thicker, as is the alloy layer, and it is much less porous. To ensure no porosity, I would suggest a tin layer of at least 10 microns (0.01mm), although you may be able to get away with 5 microns. Any less will have porosity. You may also want to lacquer the tin coating with a polyacrylic resin or something similar as this will add protection.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003