Sodium hexafluoroaluminate is also called cryolite, which molecular formula is Na3AlF6. With excellent properties, it is not only an indispensable co-solvent in the aluminum smelting industry, but also widely used in other industries, such as opalizers in the enamel industry, opacifiers in the glass industry, and wear-resistant fillers in the rubber and grinding wheel industries.
Sodium hexafluoroaluminate is mainly used as a flux for aluminum electrolysis, and also as a wear-resistant additive for grinding products, which can effectively improve the wear-resistant cutting force of the grinding wheel and prolong its service life and storage time. It is a flux for ferroalloy and boiling steel, non-ferrous metals and soldering materials, a deoxidizer for casting, a catalyst for olefin polymerization, and an anti-reflective coating and opacifierfor glass, an emulsifier for enamel, a filler for ceramic industry, and a pesticide for agriculture, etc.
Sodium hexafluoroaluminate is rarely produced in nature and is usually manufactured artificially. Its consumption in the aluminum industry is large, and the annual consumption in the world is about 700,000 tons. As a flux for electrolytic aluminum smelting, it must meet certain requirements in terms of sodium to aluminum molecular ratio, impurity content, and water content.
(1) The ratio of sodium to aluminum in cryolite should be as high as possible. The higher the molecular ratio, the higher the current efficiency of electrolytic aluminum smelting, the less fluorine loss, and the less environmental pollution it causes. Moreover, sodium hexafluoroaluminate with high molecule ratio is more suitable for use in industries other than the aluminum industry.
(2) The content of impurities such as silicon oxide, iron oxide and phosphorus pentoxide in cryolite is low. These impurities will directly affect the quality of aluminum ingots and the current efficiency of aluminum smelting.
(3) The water content of sodium hexafluoroaluminate should be as low as possible. Water will increase the consumption of cryolite.