Corrosion behavior of TIG welded joints of 316L stainless steel in H₂S solutions

316 L stainless steel welded joints was prepared by tungsten-arc inert gas (TIG) welding. The corrosion behavior of the TIG welded joints of 316 L stainless steel in different concentrations of H₂S solutions are studied by polarization curves, electrochemical impedance spectroscopy (EIS), Mott-Schottky plots, and immersion corrosion experiments. Polarization curves and EIS results show that the corrosion current densities of the joints significantly increased as the concentration of H₂S solutions increasing, while the corrosion potential decreased. Additionally, for the samples in the same concentration of H₂S solutions, the 316 L base material shows the lowest corrosion current densities, next is the heat-effected zone, the welded zone presents the highest corrosion current densities. Mott-Schottky plots show that the passive films appear a p-n heterojunction, and the donor and acceptor densities reach 1 022 cm^-3, showing a highly defective character of the passive film. The donor and acceptor densities increase with increasing H₂S concentrations. The decreased passivity and the increased doping density affect the protectiveness of the passive film toward corrosion.