The use in industry of molten salt baths for the heat treatment of metals is an important process with a number of unique advantages. Depending on the nature of the salt used, the bath may be simply a heat-transfer medium (nitrate tempering treatments, chloride austenitizing baths) or a high-temperature chemical processing system (cyanide treatments) where reactions within the bath and at the surface of the treated part result in fundamental structural changes in the part with, in particular, enhancement of surface hardness and wear resistance.