Silver/Tin whiskers
Under certain environmental conditions, contamination by hydrogen sulphide (common in sewage works, for instance) will grow what look like whiskers on tin plated surfaces. They can grow amazingly fast and long. This is not great for anything containing electrickery. The effect on 400V gear is truly explosive.
Pictures etc here:- https://en.wikipedia.org/wiki/Whisker_(metallurgy)
Biting the hand that feeds IT
