Effect of laser surface hardening on pitting corrosion resistance of AM50 magnesium alloy

The influence of laser shock processing (LSP) on pitting corrosion of AM50 magnesium alloy in chloride solution was evaluated. Bright shallow dimples were formed after laser shock processing, and surface changes were accompanied by small roughening effects. Plastic deformation occurred and compressive residual stress formed in the surface layer. The compressive residual stress on the surface reached 146MPa with laser power density of about 3GW/cm². The electrochemical polarization curve showed that the corrosion potential and pitting potential of the LSP sample increased 85mV and 153mV as compared to the untreated sample, respectively, while the corrosion current density was about one order of magnitude lower. After 5 hours immersing in the chloride solution, many pits appeared on the surface of untreated samples, while few pits appeared in the LSP samples. The pitting corrosion resistance of the LSP AM50 was improved significantly; a beneficial influence of laser surface hardening has been demonstrated.