THE ACTIVATION OF ALUMINUM BY ACTIVATOR ELEMENTS

In this communication, the results of an investigation into the activa tion of aluminium electrodes by metal salt solutions, using potentiost atic current-time measurements, are described and discussed. Activator salt was added to the aggressive test halide electrolyte after a give n passivation period and the current flowing at the electrode was moni tored as a continuous function of time. Prior to the detection of acti vation, as current fluctuations in the potentiostatic measurements, an induction period, found to be a measure of the rate of initiation of attack, was observed. This induction period appears to be a critical p henomenon associated with the build-up of a sufficient concentration o f deposited activator complex on the test electrodes to facilitate the onset of attack. For a given applied passivation potential, it is pro posed that the role of deposited activator is to 'bias' the surface ch arge in the direction of activation, and that activation occurs only w hen sufficient bias has been achieved. Since halide adsorption occurs more readily at the biased surface, attack of the electrode proceeds t he more readily.