Effects of film formation parameters on stress generation during anodic oxidation of metals in corrosive media

Abstract

Stresses generated during the anodic oxidation of metals in aqueous solution were measured as a function of applied current density, potential step and chloride ion concentration by using a beam deflection technique. In the absence of chloride ion, the stresses which amounted to a few GPa were developed in the oxide film and were mainly composed of the volume-generated stress and electrostrictive stress components. The transition from compressive to tensile deflection occurred at applied current densities of 0.05 and 0.10 mA cm −2. The compressive stresses developed in films grown in chloride ion-containing solutions amounted to about 10 times larger than those in films grown in chloride ion-free solutions. In the presence of chloride ion, before the oxide film breakdown, specimens moved increasingly in a compressive direction with increasing chloride ion concentration. In contrast, after the oxide film breakdown, the reverse movement in a tensile direction was encountered and the deflection rates increased with increasing chloride ion concentration. The changes in the sign and magnitude of deflection in the absence/presence of chloride ion are well accounted for in terms of the relevant reactions occurring both at the metal/oxide and at the oxide/electrolyte interfaces during the oxide growth.