Stability of passive film on 13Cr tubing in impurity-containing supercritical CO2 injection well environments

The integrity of CO 2 injection wells is crucial for the long-term safety of carbon capture, utilization, and storage (CCUS) technology. This study investigated how impurities such as H 2 S, SO 2 , and O 2 affect the passivity and localized corrosion of 13Cr stainless steel (SS) under simulated injection well conditions (30 MPa, 80 °C), via high-temperature and high-pressure (HTHP) corrosion simulation experiments, coupled with surface characterization techniques, including 3D profilometry, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and simulation calculations. Results show that the stability of the passive film decreases with the increase in impurity types in the CO 2 fluid. 13Cr SS remains passive in the impurity-free supercritical CO 2 system, while all impurity-containing systems induce localized attack, with the most severe corrosion in the CO 2 -O 2 -SO 2 -H 2 S system. The presence of impurities and their interactions significantly enhances the corrosivity of the wellbore environment. On the one hand, trace amounts of HS - and S 2- formed by the hydrolysis of H 2 S tend to induce an increase in defects within the passive film. On the other hand, elemental sulfur and H 2 SO 4 produced by reactions among impurities lead to a significant decrease in the system pH, resulting in a marked increase in the passive current density of 13Cr SS in the multi-impurity system. With increasing impurity types, the main components of the passive film, originally composed of Fe 2 O 3 , Cr 2 O 3 , and Cr(OH) 3 , are gradually doped with corrosion products such as FeS 2 , FeS, FeSO 4 and FeOOH, leading to a progressive decline in its stability.