The electrochemical behaviors of 304 stainless steel before and after mechanical surface treatment were investigated by electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution. Prior to EIS measurements, potentiodynamic polarization was conducted to characterize the passive potential range and localized potential behaviors. The potentiodynamic polarization results demonstrated a localized corrosion potential shift towards a more noble direction and an expanded passive potential range after the shot peening process. The EIS results showed that the surface barrier of 304 stainless steel improved after the shot peening process. In addition, field emission scanning electron microscopy (FE-SEM) observations revealed grain refinement on the 304 stainless steel surface after the shot peening process. The observed improvement in localized corrosion resistance may be attributable to grain refinement of the 304 stainless steel surface.
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