A Study of the Formation and Dissolution of Porous Anodic Oxide Films on Aluminum: Behavior of the Porous Layer

Abstract

The formation and dissolution of porous alumina films in sulfuric acid was studied by the incorporation of the radiotracer into the film during preparation. The results have shown that (a) the formation site of the porous oxide is the barrier layer‐porous layer interface, (b) the dissolution time for porous films is independent of thickness. Comparison with former work, on "duplex" barrier films, suggests a method of identifying barrier and porous type films. By the use of "duplex" films, dissolution studies have shown that a simple pore widening mechanism of dissolution is incompatible with the results. A pore widening‐concurrent pore shortening dissolution mechanism based on a truncated pore model is proposed, and has been found to be experimentally valid.