Current Efficiency, Corrosion and Structural Changes in SnO₂-Sb₂O₃-CuO Inert Anodes for Aluminium Electrolysis

A systematic study was conducted on current efficiency (CE), corrosion and structural changes in SnO₂-based inert anodes (made of 96wt%SnO₂+2wt%Sb₂O₃+2wt%CuO) on a laboratory Hall-Heroult aluminium cell. The influence of operating parameters and elec-trolyte composition on the CE and corrosion process were evaluated. The CE was found to be more than 90% and catastrophic corrosion took place at low percent of Al₂O₃, high percent of LiF, low cryolite ratio and high current densities. From all the structural changes that took place in the SnO₂-based inert anodes, we assumed that the most important contri-bution was due to the migration of CuO towards the outer limits of the constituent grains of SnO₂ based ceramic. The complex process occurred during the formation of various phases and their sintering ability both directly depended on Cu/Sb molar ratio.