Abstract:New types of refractory materials need to be developed for designing the man-made ledge of the Hall-Héroult cell for aluminum electrolysis, which are currently constructed by frozen ledge. Magnesium aluminate spinel (MAS) as potential candidate materials was prepared by two-step sintering. The densification and grain growth of the MAS were investigated by the Archimedes drainage method and scanning electron microscope (SEM). All the specimens were corroded in a Na₃AlF₆-AlF₃-CaF₂-Al₂O₃ bath to assess the corrosion resistance. The results show that a MAS material with a high relative density of 99.2% and a homogeneous microstructure is achieved under two-step sintering conditions. The corrosion mechanisms of MAS in Na₃AlF₆-AlF₃-CaF₂-Al₂O₃ bath are mainly proposed by dissolution of MAS, formation of aluminum oxide, and diffusion of fluorides. The MAS prepared by two-step sintering exhibits good corrosion resistance to the Na₃AlF₆-AlF₃-CaF₂-Al₂O₃ bath.

Key words: magnesium aluminate spinel; sintering; aluminum electrolysis; corrosion resistance