Ledge-free sidewall is preferred as it potentially reduces the energy requirement of aluminium production by about 30%. However, this approach poses great material challenges because such sidewalls are in direct contact with oxidizing, corrosive and reducing environments at different cell locations. In this study, NiAl2O4, MgAl2O4 and Ni0.5Mg0.5Al2O4, were identified and tested in cryolite-AlF3-Al203-CaF2 electrolyte melts at 980°C under air and CO2. Both specimens and baths were characterized using XRD, XRF and SEM-EDS methods. This study revealed that the NiAl2O4 and MgAl2O4 spinels had good corrosion resistance toward the melts under CO2, with solubility of Ni from NiAl2O4 being 0.01wt% and Mg from MgAl2O4 being 0.07wt%. Dissolution of Ni and Mg into the bath was lowered to 0.007wt% Ni and 0.05wt% Mg through the formation of a Ni0.5Mg0.5Al2O4 solid solution.
Light Metals 2011: proceedings of the 140th Annual Meeting and Exhibition of the Minerals, Metals and Materials Society (TMS 2011), San Diego, United States, 27 February-03 March 2011 / Stephen J. Lindsay (ed.),