Stress generation during anodic oxidation of titanium and aluminum

Stresses generated during the anodic oxidation of titanium and aluminum were measured using a bending cantilever beam technique. The compressive deflection due to electrostriction was found to increase linearly with potential during oxide growth. Slowly grown oxides had greater electrostrictive deflections than more rapidly grown oxides. Tensile stress develops at the metal/oxide interface due to the volume difference between the metal ionized and the oxide formed at that interface. The sign and magnitude of the volume-generated stress is related to the Pilling-Bedworth ratio of the metal and the transport number of the anion in the oxide. A general model for stress development is developed and applied to other systems.