The rate of oxygen evolution on metallic inert anodes was measured as a function of current density during electrolysis of a low-melting NaF(12)-KF-AlF(3) bath ([NaF + KF]/[AlF(3)] = 1.5 mol mol(-1)) at 800 A degrees C. The oxidation rate of the anode substrate (A cm(-2)) was calculated. The anode oxidation process was depressed at the potentials of oxygen evolution. The dynamics of the decrease in the oxidation rate, which were obtained in previous study by the change in geometrical size of the metallic part of the specimen, was reproduced both by the technique proposed and also in potentiostatic electrolysis at potentials below that of oxygen evolution, in some cases, depending on prepolarisation.