ELECTROCHEMICAL STUDIES ON WETTABILITY OF SINTERED TIB2 ELECTRODES IN ALUMINUM ELECTROLYSIS

Electrochemical studies have been conducted to better understand the behaviour of sintered TiB2 cathodes in cryolite-alumina melts. Cyclic voltammetry has also been used to identify the origin of the cathodic prewaves seen when the electrodes are cycled in the unsaturated melts. These cathodic prewaves have been attributed to the reduction of TiO2 and B2O3 formed during anodic scanning of the TiB2. Furthermore, microprobe analysis work has shown that the sintered TiB2 substrate is susceptible to penetration by the melt components. This has been seen to affect the long-term wetting properties of the substrate by affecting the surface in contact with the molten bath. It has also been seen that subjecting the electrode to controlled oxidation for long periods results in a black deposit formation on the TiB2 surface, and this hinders the aluminium deposition process, particularly in the alumina-saturated melts. The overall wetting properties of TiB2 have been compared to those of graphite as these two materials are the principal components of the TiB2/C composite cathodes that are being investigated for use in low energy aluminium electrolysis cells.