Insight on corrosion behavior and mechanism of AA2219 friction stir welded joint in N2O4 medium

This paper investigated the corrosion behavior of AA2219 friction stir welded joints in N2O4. The results showed that with the extension of immersion time, corrosion behaviors such as pitting, intergranular corrosion, and exfoliation corrosion occurred in both base material and weld nugget zone, but there are differences in corrosion sensitivity, and the corrosion behavior mechanism and corrosion sensitivity differences were further analyzed. Pitting was caused by the dissolution of the aluminum matrix near the intermetallic Al2Cu. In addition to the potential differences, intergranular corrosion was also related to grain boundary misorientation and differences in grain boundary precipitates. Corrosion products observed visually at the intergranular corrosion position were helpful in understanding the corrosion mechanism. This work is the first to systematically investigate and report the evolution in corrosion behavior and mechanism of AA2219 FSW in N2O4, which can be a reference for the study of aerospace aluminum alloy materials.