Corrosion resistance of high-strength modified 13 % Cr steel

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Corrosion resistance of high-strength modified 13 % Cr steel

Kimura, M. / Miyata, Y. / Yamane, Y. / Toyooka, T. / Nakano, Y. / Murase, F.

A new 13% Cr martensitic stainless steel (0.025% C-13% Cr-Ni-Mo) with excellent resistance to carbon dioxide (CO2) corrosion and good resistance to sulfide stress cracking (SSC) was developed, and its application limits in oil and gas environments were clarified. The CO2 corrosion rate of the 13% Cr steels with Ni and Mo was < 0.3 mm/y at 180 deg C (356 deg F) in 20% sodium chloride (NaCl). It was less than that of the conventional 13% Cr steel (0.2% C-13% Cr). The corrosion rate of the steel slightly decreased with the increase in Mo and Ni content. The SSC resistance improved with the increase in Mo content. The critical partial pressure of hydrogen sulfide (H2S) for the 2% Mo steel was > 0.005 MPa at pH 3.5. Effects of Ni and Cu on SSC were not distinctive for this kind of steel. These results depended upon hydrogen permeability. The ciritcal H2S partial pressure for the 110-grade steel was the same as that of the 95-grade steel at pH 4.5 and pH 3.0 and was slightly lower at pH values between 3.0 and 4.5. The new 13% Cr steel proved to have excellent properties in the sweet and slightly sour environments.