The electrochemical behaviour of 316L austenitic stainless steel in Cl− containing environment under different H2S partial pressures

In oil-gas production environments, presence of H2S-Cl− can induce deterioration of the passive film, leading to pitting corrosion of stainless steels. In this paper, by using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and capacitance measurements (Mott-Schottky analysis), the electrochemical behaviour of AISI 316L austenitic stainless steel was investigated in Cl− solutions under different H2S partial pressures (from 0 to 1.0 bar). The results indicated that presence of H2S in Cl− solution can accelerate both the cathodic and anodic current density, leading to a metastable passive state in higher passive potential range, changing the semiconductor behaviour from p-type to n-type, increasing its susceptibility to corrosion. XPS analysis was employed to characterize the surface film after potentiostatic polarization, whose results provide good evidences for the electrochemical measurements.