Stability of Chlorides in Cryolitic Electrolyte

Chloride is considered one of the most important contaminants in cryolitic electrolyte system for aluminum smelting, and yet at the same time, chloride salts such as NaCl, MgCl2 and others have also been chosen for potential additives to change the electrolyte physical chemical properties for smelting efficiency improvement. This paper studied the chloride stability in the cryolitic electrolyte system. The behavior of NaCl and MgCl2 was investigated when there is a moisture present with or without electrolysis or when there is anode effect. HCl will be generated along with HF during a normal electrolysis even when chloride in the electrolyte is at a low level. CF3Cl gas is generated along with CF4 and CxFy when anode effect occurs. The results confirm that even though chlorides (NaCl/MgCl2) are considered the most important contaminants, the level of the contaminants remains relatively low in the smelting electrolyte without obvious accumulation over time.