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Corrosion behavior of 3 wt.-% Chromium (3Cr) tubing steel in CO2 saturated high-salinity brine was investigated by using an autoclave in the laboratory. The partial pressure of CO2 and the Cl− concentration were fixed at 0.2 MPa and 139552 mg × l−1, respectively. The water cut was varied from 20 to 100 vol.-%, and the temperature was varied from 50 to 110 °C. For comparison, the corrosion behaviors of N80 carbon steel and 13 wt.-% Cr (13Cr) martensitic stainless steel were tested in the same conditions. The surface morphologies and chemical composition of corrosion product layers were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry (EDS) technologies. The results show that the 3Cr steel's corrosion rate increased as water cut increased, especially when the water cut exceeded 70 vol.-%. Serious general corrosion and local attack occurred on the 3Cr samples in a 0.2 MPa CO2 and 139552 mg × l−1 Cl− corrosion environment. The product layer structure of 3Cr steel in high-salinity brine is demonstrated. When the chloride ion concentration is high enough, the Cr-enriched layer no longer provides sufficient protection against the chloride ion penetration and pitting attacks may occur.

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