ISSN: 1003-6326
CN: 43-1239/TG

Vol. 26    No. 10    October 2016

Two-step sintering of magnesium aluminate spinels and their corrosion in Na3AlF6-AlF3-CaF2-Al2O3 bath
Jian-hua LIU, Xiao-jun Lü, Jie LI, Ling-yun HU, Liang-xing JIANG
(School of Metallurgy and Environment, Central South University, Changsha 410083, China)
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
Superintended by The China Association for Science and Technology (CAST)
Sponsored by The Nonferrous Metals Society of China (NFSOC)
Managed by Central South University (CSU)