Electron Microscope Study of Breakdown and Repair of Anodic Films on Aluminum

Abstract

In films forming in , many breakdown events including pit initiation were found to occur continually but to be followed by almost immediate repair, so that the stability of film growth was due not to the absence of breakdown but to the efficacy of repair. A relation between the sites of breakdown and substrate structure was not indicated. Film growth was interpreted as occurring through a compact film at pore bases, as in the classical mechanism, and also through breakdown—extension of a pore near to the metal interface—and repair by reanodization to form a hemisphere of compact film extending into the substrate. An interpretation of the geometrical structure of the film is proposed.