THE EFFECT OF OXIDE CHEMISTRY ON THE PASSIVITY OF ALUMINUM SURFACES

The present work is concerned with the effect of oxide chemistry on the passivity of aluminium surfaces. A plasma-enhanced chemical Vapor deposition (PECVD) method was employed to obtain aluminium oxide films with a similar chemical composition to that of the surface oxide films. The chemical composition of the PECVD-aluminium oxide films obtained at different deposition temperatures was identified by using static secondary ion mass spectroscopy (SSIMS). Based upon the results of SSIMS, analysis of the results of A.C.-impedance and cathodic polarization measurements demonstrated that AlO(OH) species contained in the PECVD-aluminium oxide films raises the corrosion resistance in deaerated acidic chloride solution. The experimental results suggest that the mechanism by which the surface oxide film loses its protective character in a chloride solution is essentially governed by the chemical characteristics of the oxide film.