Corrosion and oxidation of silicon carbide on the nitride bond in the side lining of aluminum electrolysis cells

Abstract

The main question for understanding the corrosion of silicon carbide on the nitride-silicon bond onboard linings is whether corrosion of Si3N4‒SiC material with gases (and, in particular, oxidation) is preceded by corrosion by molten electrolyte, or corrosion by molten electrolyte plays its own role in material degradation during service. It is more likely that the reactions of SiC and Si3N4 with cryolite melt pass through a preoxidation stage. Calculations show that most of the possible reactions of SiC and Si3N4 with oxygen and carbon monoxide and carbon dioxide have a positive volumetric effect, which reduces the porosity of the material, but may cause cracks in it. The resulting silicon oxide is dissolved in the electrolyte melt, and can also react with electrolyte components in the gas phase. Ill. 6. Ref. 24. Tab. 2.