Corrosion behavior of novel 2Cr1Mo2Ni steel in the oil field formation water containing CO₂

The corrosion behavior of the new 2Cr1Mo2Ni steel in the oil field formation water containing CO₂ at 80℃ and 0.8 MPa was studied herein to clarify the role of Ni and Mo in the corrosion resistance of low-Cr steel. The surface morphology and the chemical composition of the corrosion scales were analyzed by scanning electron microscopy and energy dispersive spectroscopy (EDS). The polarization curves and the electrochemical impedance spectroscopy spectra were also obtained to explore the growth process of the corrosion scale. The results indicate that Mo and Ni are not as efficient as Cr in enhancing the corrosion resistance of the low-Cr steel. The low-frequency inductance loop disappears after 164 h immersion. Moreover, the corrosion scale completely covers the substrate surface. In addition, the protective corrosion scale forms after 240 h immersion.