Transition from intergranular to pitting corrosion in fine grained aluminum processed by equal channel angular pressing

• Equal Channel Angular Pressing (ECAP) refines grains and inclusions in aluminum.
• A tendency to passivation is generally obtained before and after ECAP.
• Transition from intergranular to pitting corrosion is observed after ECAP.
• Inclusion crushing increases low depth pit density in spite of to deep pits.

Equal Channel Angular Pressing (ECAP) is used to improve the strength of metallic materials by grain refinement. Moreover, extensive applications become possible by combining high strength with good surface properties. In the present work, the effect of ECAP on the corrosion behavior of aluminum was investigated in a 3% NaCl medium. From electrochemical experiments, microscopic and topographic observations, we have shown that, corrosion is mainly intergranular in the coarse grained material. After ECAP, a clear pitting is observed. We related this to a destruction of the preexisting grain boundaries and to the homogenization of the microstructure achieved by ECAP.