Pitting and Uniform Corrosion of Aluminum by pH 3.5 Citrate Buffer Solution

Abstract

Corrosion of 3003 aluminum in citrate buffer solution in the presence of air may be by pitting or by uniform attack. Polarization data indicate that uniform attack is controlled by the rate of chemical dissolution of the oxide film. There is a simultaneous thickening of the film by a tarnishing‐type reaction at the same rate to maintain the film at constant thickness. Values of ΔD/ΔE determined from polarization data at constant potential were indicated to be the same for a film being formed principally by the tarnishing mechanism as for a film being formed entirely by anodic action. It was found possible to determine whether or not pitting was occurring from anodic polarization data.