Beneficial role of retained austenite in pitting corrosion resistance of Fe-C-Si-Mn steel in chloride environments

The pitting corrosion behavior of Fe-0.39C-1.51Si-2.01Mn steel was investigated in NaCl-containing boric-borate buffers at pH 7.0. The microstructure of the steel was confirmed to consist of retained austenite and bainite matrix, and the interstitial C concentration in the retained austenite was estimated to be higher than that in the matrix. The results of immersion tests clarified that the retained austenite hardly dissolved in the early stage of pitting, and acted as a barrier against pit propagation. The dissolution resistance of the retained austenite appeared to originate from the high amount of interstitial C. •The pitting corrosion resistance of Fe-C-Si-Mn steel was investigated.•The retained austenite hardly dissolved, and acted as a barrier against pit propagation.•The superior dissolution resistance of the retained austenite was attributed to interstitial C.