Documented evidence of significant metal loss in aluminum crevice corrosion

Crevice corrosion of aluminum has been studied extensively and several explanations of the mechanism have been proposed. However, evidence of significant metal loss due to aluminum crevice corrosion is not well documented. This paper shows evidence of significant corrosion of aluminum within a crevice. The crevice corrosion of high purity aluminum (99.999 wt. % Al) in neutral and mildly acidic solutions was investigated. Polarization curves were generated in simulated crevice solutions and potentiostatic crevice corrosion experiments with varying crevice gap opening dimensions were performed. Current was measured and in situ photographs of the developing crevice corrosion were obtained. Crevice corrosion of aluminum in a pH 6, 0.6M NaCI solution was not found to occur under open circuit or polarized conditions. Crevice corrosion was observed for aluminum in a mildly acidic (pH 3), chloride free solution. In this solution, crevice corrosion resulting in severe material loss was observed and a high current (10 mA) was measured. The corrosion occurred in the absence of pitting corrosion. The cause of corrosion in this case could be explained by alkalization of the crevice due to a high rate of hydrogen evolution reaction, driven by a potential drop within the crevice.