Corrosion performance and mechanical properties of friction stir welded AA2024-T3 joints under different corrosion solution exposure

Aluminum alloy 2024-T3 sheets were friction stir welded (FSWed) and the microstructure in the thermo-mechanically affected zone (TMAZ) and stir zone (SZ) were characterized. The effect of corrosion exposure on the joints was evaluated under different solutions (3.5wt% NaCl, 3.5wt% NaCl+1wt% HCl, and exfoliation corrosion-EXCO) by immersion tests as well as electrochemical measurements; specimens with pre-corroded joints were subjected to tensile testing. The results indicate that TMAZ and SZ of the FSWed joints present different corrosion performances for the three corrosion solutions. SZ shows higher corrosion resistance than TMAZ, as the dissolution of precipitates in SZ considerably decreases its susceptibility to corrosion. The joint exposed to the EXCO solution has suffered higher mechanical properties degradation than the other two solutions, while the corrosion resistance of SZ and TMAZ was associated with the presence of the S-type precipitates and the concentration of H+ and Cl- ions.