ELECTROCHEMICAL STUDY OF DISSOLVED ALUMINUM IN MOLTEN NAF-ALF3-AL2O3

The oxidation of dissolved metal in acidic cryolite melts has been studied at tungsten, classy carbon and graphite electrodes using the techniques of cyclic voltammetry and chronopotentiometry. The reaction was found to be diffusion controlled and quasi-reversible with n = 2, suggesting that monovalent aluminium is the main dissolved species in acidic melts. A value of C(m)D(m)1/2 = 5.1 x 10(-7) mol cm-2 S1/2 was obtained in an alumina saturated melt at 977-degrees-C in the absence of a metal pad, while in the presence of an aluminium pad C(m)D(c)1/2 is of the order of 10(-6) mol cm-2 S1/2 suggesting that other species such as dispersed metallic aluminium are also involved.