Dissolved Metal Species Mechanism for Initiation of Crevice Corrosion of Aluminum: I. Experimental Investigations in Chloride Solutions

Experiments on initiation of crevice corrosion were carried out on A1 specimens in dilute aqueous NaCI solutions at ambient temperature. Transient current distributions within crevices were measured by a sectioned electrode technique, and microsampling was used to monitor dissolved aluminum, pH, and [Cl⁻] composition changes within the crevice prior to breakdown. Auxiliary (noncrevice) experiments were carried out in solutions having various pH, [Cl⁻], and dissolved aluminum concentration. Initiation was found to occur upon exceeding a minimum concentration of dissolved aluminum inside the crevice. Mechanisms for initiation based on acidification within the crevice were excluded.