Molten salt refers to a salt that is in the
liquid phase that is normally a solid at standard
temperature and pressure (STP). A salt that is
normally a liquid at STP is usually called a room
temperature ionic liquid, although technically
molten salts are a class of ionic liquids (ILs).
Molten salts have a variety of uses. Molten
chloride salt mixtures are commonly used as
baths for various alloy heat treatments, such as
annealing and mar tempering of steel. Cyanide
and chloride salt mixtures are used for surface
modification of alloys such as carburizing and
nitro carburizing of steel. Cryolite is used as a
solvent for aluminum oxide in the production of
aluminum.