Formation Efficiency of Porous Oxide Films in Aluminum Anodizing

Abstract

Anodic oxidation of aluminum in acidic electrolytes is widely used for the formation of porous oxide films with a regular structure on the metal surface. Despite the century-old history of this process, the mechanism of channel ordering into a 2D hexagonal array is still not entirely clear. This work studies the modes of porous oxide film formation in 0.3 M oxalic acid at the anodizing voltages of 20 to 130 V and in 0.3 M sulfuric acid in the range of 19 to 60 V. The mass fraction of electrolyte impurities in the anodic aluminum oxide (AAO) structure, the formation efficiency, the volume expansion factor of the material in anodizing, and oxide film porosity are determined for the given conditions. The wide range of applied anodizing voltages allowed establishing a relationship between the degree of ordering of porous structures and the formation efficiency of anodic alumina and volume expansion of the material.