Re: Zinc Pest was Re: Times have changed!

Tony Thompson

Craig Zeni wrote:

Back in my college days when I was studying metallurgy, one of my professors who happened to be a tinplate train collector and restorer told me his theory was that poison Zamac aka zinc pest isn't an electrolytic problem or a corrosion problem or a temperature problem. It's an atomic problem, a metallurgical problem with impurities - typically lead, antimony and bismuth.
Well, that theory takes a hit from the fact that humidity greatly accelerates zinc pest. It is always cited in metallurgical sources as a corrosion problem, and is certainly due to the impurities, primarily lead. Since 1960, when this problem became well understood, zinc and zamac castings are usually okay. Earlier ones, some fail, some don't. I have a few old pairs of trucks from the 1950s, and in two of the pairs, one has crumbled, the other looks fine (and yes, now I have one good pair out of the two).

Tony Thompson
Retired metallurgist , corrosion scientist, and professor of materials science

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