Regulating solute partitioning via submerged friction stirring technology for improving corrosion resistance in an AlMg alloy

Recently, compared to friction stirring processing (FSP) conducted in air, the potential of submerged FSP (SFS) for enhancing mechanical properties by immersing the workpiece in water has garnered significant attention. However, this enhancement was achieved at the expense of the corrosion resistance of alloys. In this study, the innovative use of a 10 wt% CaCl2 solution as a medium (SFS(CaCl2)) was expected to improve the corrosion resistance. Electrochemical tests conducted in 3.5 wt% NaCl solution showed that SFS(CaCl2) treatment improved the corrosion resistance of alloy compared to FSP treatment, including its contribution to pitting resistance. By summarizing the characteristics of microstructure, the mechanism of excellent corrosion resistance for SFS(CaCl2) sample was explained in detail. Nanoscale microstructure played a decisive role. By atomic-resolution TEM, the SFS(CaCl2) samples uniquely formed homogeneous clusters (1– 2 nm). The high-density clusters reduced the size of the solute depletion zone, and homogenized the local strength of the microstructure.