Low C MSSs (martensitic stainless steels) have been widely used for oil country tubular goods and line pipe because of their high strength and excellent corrosion resistance in CO 2 gas wells. Recently, much attention has been paid for application of these steels in light sour environments. Effects of pH and PH2S (Partial pressure of H2S) on SSC resistance of low C MSSs are studied. Effects of chemical compositions on depassivation pH are also studied. Uni-axial constant load test of some low C MSSs in solutions of pH=3.5-4.5 with PH2S=0.035-1atm were conducted. When pH is lower than depassivation pH, these steels
show poor resistance to SSC. When pH is higher than depassivation pH, SSC resistance of these steels depends on PH2S. One method of improving SSC resistance of low C MSSs is reducing depassivation pH of steels. Mo is considered to be an important element to reducing depassivation pH of low C MSSs in CO2 and H2S environments.
Keywords: Martensitic stainless steel, pH, H2S, SSC