Corrosion resistance of additively manufactured 316L stainless steel in chloride-thiosulfate environment

In this paper, synergistic effects of chloride (Cl-) and thiosulfate (S2O32-) on corrosion resistance of additively manufactured (AM) and wrought 316L stainless steel (SS) were investigated in ammonium chloride (NH4Cl) solution in the absence and presence of different concentrations of sodium thiosulfate (Na2S2O3). General corrosion induced by Cl- accelerated with the increase of S2O32- concentration for both of the samples. However, pitting resistance of AM 316L SS was found to be at least 4- to 6-fold higher than that of the wrought sample depending on S2O32- concentration. The AM sample demonstrated significantly improved metastable pitting resistance in the presence of S2O32- into Cl - solution. In addition, the passive film of AM 316L SS offered higher charge transfer resistance and film resistance confirming its better stability and barrier characteristics in Cl-S2O32- environment. The superior corrosion resistance of AM 316 L SS compared to wrought sample was attributed to refined microstructure, absence of MnS micro-inclusions, and lack of Cr depleted regions. (C) 2020 Elsevier Ltd. All rights reserved.