Corrosion resistance improvement on 316L stainless steel using humidity-assisted nanosecond laser pulses

A novel method for enhancing the corrosion resistance of 316L stainless steel was investigated using nanosecond laser pulses in a high-relative humidity environment. The effects of parameters relative humidity level, overlap rate, and irradiation fluence on 316L stainless steel’s breakdown potential and impedance were studied. Increasing the overlap rate and the fluence initially increased the breakdown potential but later reduced it as both parameters increased further. A higher level of relative humidity significantly enhanced the breakdown potential and impedance. Significant positive breakdown potential above 1.0 V (Ag/AgCl) with good repeatability was achieved at the optimal laser irradiation parameters under the humidity level of 95%. Based on the microstructure and composition analyses, the oxide film formed with modifications such as compactness, film thickness, and high relative content of chromium oxide by the laser irradiation in a humidity environment. These modifications were responsible for the significant enhancement of corrosion resistance.