Growth peculiarities of aluminum anodic oxide at high voltages in diluted phosphoric acid

The growth of porous aluminium anodic oxide films on 99.5%, 99.99% and 99.9 99% purity Al metal in stirred dilute phosphoric acid solutions (0.005-0.4 mol l(-1)) at 2-20 degreesC temperature and relative high anodizing voltage s was studied. A kinetic model is proposed for solutions of concentration u p to 0.1 mol l(-1). The size of cells in the films formed in dilute phospho ric acid solution varies linearly with the anodizing voltage with a proport ionality coefficient varying from 2.67 to 2.25 at electrolyte concentration s from 0.2 to 0.025 mol l(-1), respectively. On the basis of the variation of oxide film mass, current density and Al volume expansion factor with ano dizing time, conditions for the formation of highly ordered pore arrays may be predicted. (C) 2001 Published by Elsevier Science B.V.