Effects of laser shock processing on corrosion resistance of AISI 304 stainless steel in acid chloride solution

The effects of laser shock processing (LSP) on corrosion behavior of AISI 304 stainless steel in acid chloride solution have been investigated using electrochemical impedance spectroscopy (EIS). Surface modifications including microstructure, residual stress, micro-hardness and phase transformation are characterized. Results show that LSP can promote the formation of deformation twins and deformation induced martensite, produce grain refinement, generate high magnitude compressive residual stress and increase surface micro-hardness. EIS results show that charge transfer resistance of one layer LSP treated sample is always higher than those of double layer LSP treated sample and non-treated sample in both acid chloride solutions, which implies a higher corrosion resistance for one layer LSP due to the formation of the compact passive film with less defects. Grain refinement and compressive residual stress induced by LSP can enhance the corrosion resistance of AISI 304 stainless steel, but the deformation induced martensite generated during LSP decreases the corrosion resistance. Corrosion resistance of AISI 304 stainless steel in acid chloride solution depends on the combined effects of these factors.