THE SELF-REGULATION MECHANISM OF PASSIVE METAL DISSOLUTION (CORROSION) IN AQUEOUS-ELECTROLYTE SOLUTIONS

A novel mechanism of self-regulation of the processes that take place during steady-state passive metal dissolution is postulated. The mechanism provides an explanation for the independence of the dissolution current of the electrode potential on the basis of the fact that the potential drop at the film-solution interface, which dominates the dissolution rate, is independent of the electrode potential, but is uniquely dependent on kinetic and dielectric parameters. The dependence on the kinetic parameters is due to the equality of the film dissolution and growth rates, which is governed by migration of oxygen anions to the metal boundary. The dependence on the dielectric constant of the film and the electric double layer, on the other hand, is due to the fact that the potential drops across these appear to be inversely proportional to their capacitances.