Pitting corrosion susceptibility of ultrafine grains commercially pure aluminium produced by accumulative roll bonding process

Abstract

Ultrafine grains (UFGs) of commercial pure (CP) aluminium were produced by accumulative roll bonding (ARB) process. The relative pitting corrosion susceptibility of a coarse grained (CG) initial sample and ARB processed samples was investigated using direct current electrochemical techniques and immersion test. Applying the ARB process for eight passes was found to significantly decrease the anodic breakdown and repassivation potentials (E _bd and E _rp respectively) of the samples. It is also postulated that the protective characteristics of passive film were diminished through the ARB process. These results were interpreted in terms of the high defects and inhomogeneities in oxide film as well as cathodic intermetallic particles (Al₃Fe and Al₆Fe intrinsic inclusions). SEM observations from the sample surfaces after the immersion test confirmed these results.