Microstructural aspects of the degradation behavior of SnO2 -based anodes for aluminum electrolysis

cZAO NTTs Bakor, Sherbinka, 142171 Moscow, Russia The performance of SnO2 ceramic anodes doped with copper and antimony oxides was examined in cryolite alumina melts under anodic polarization at different cryolite ratios, temperatures, times, and current densities. The corroded part consists of a narrow strong corrosion zone at the anode surface with damage of the intergrain contacts and a large increase in porosity, a wider moderate corrosion zone with a smaller porosity increase, and a Cu depletion zone, where the ceramic retains its initial microstructure and a slight porosity increase occurs due to the removal of the Cu-rich inclusions. Mechanical destruction of the anode was never observed in the 10–100 h tests. A microstructural model of the ceramic was suggested, consisting of grains with an Sb-doped SnO2 grain core surrounded by an 200 to 500 nm grain shell where SnO2 was simultaneously doped with Sb and M n+