Abnormal Evolution of Pitting Behavior of Warmly Pre-Strained Austenitic Stainless Steels

The effect of warm pre-strain on the corrosion behavior of 304 and 316 steels in 3.5% NaCl solution was first explored by electrochemical tests, passive film characterization, and structural analysis. The pitting corrosion resistance of 304 steel decreases with the increase of strain level below 20% and increases with the strain at a higher strain level, while the pitting corrosion resistance of 316 steel increases slightly with the increase of strain level below 20% and decreases with the strain at a higher strain level. The random grain boundaries in 304 steel are interrupted with the increase of strain level higher than 20%; this does not occur in 316 steel, which exhibits more dislocations. The coupling effect of microstructure changes induced by warm pre-strain affects the oxide content of the passive film, especially for the chromium oxide, which results in abnormal corrosion behavior. Knowing the corrosion mechanism is of value for academic research and enables the design of advanced stainless steel with high strength and corrosion resistance.