COMPARISON OF THE BEHAVIOR OF GLASSY-CARBON AND SOME METALS FOR USE AS NONCONSUMABLE ANODES IN ALUMINA CRYOLITE MELTS

Current interest exists in development of nonconsumable anodes for the Hall-Heroult process of aluminium production and also in situ analytical probes for determination of Al2O3 content in the cryolite melts used in this process. A comparison of the behaviour of glassy carbon and metals such as tungsten, tungsten carbide, nickel and stainless steel (SS-316) used as anodes in alumina-cryolite melts is investigated by means of electrochemical transient techniques (cyclic voltammetry and chronoamperometry) and Tafel anodic polarization experiments. The results show that only glassy carbon could be used as a successful sensor electrode for an in situ determination of Al2O3 in alumina-cryolite melts and that the metals investigated are unresistant to anodic attack in such melts. Consequently, the metals investigated cannot be used as sensor electrodes for bl situ electroanalytical determination of alumina in alumina-cryolite melts, nor as anodes in the production of aluminium by the Hall-Heroult process.