Corrosion and metallurgical investigation of two supermartensitic stainless steels for oil and gas environments

• Two supermartensitic stainless steels are characterized.
• The 17-4 PH stainless steel is more susceptible to sulfide stress corrosion cracking.
• Low depassivation pH in H2S media is found for 1.4418 grade.
• The pitting corrosion resistance is slightly improved by the retained austenite.
• The retained austenite plays no role on sulfide stress cracking.

The corrosion properties of two supermartensitic stainless steels were studied in chloride and H2S environments. A comparison between 1.4542 and 1.4418 SS grades was made considering the effects of microstructure, different steps of the heat treatment on the pitting and sulfide stress cracking SSC properties. The SSC limits of 1.4418 were determined in terms of different pH and PH2S conditions. In H2S media, the 1.4418 presented a higher stability and passivation compared to 1.4542. The Electron back-scattering and X-ray diffraction were used to characterize the amount of’ retained austenite in the 1.4418 and then its influence on pitting and SSC resistance was investigated.