Halogenated bis-Schiff bases as corrosion inhibitors in high-temperature and high-pressure CO2/O2 environments

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During the application of carbon capture, utilization, and storage (CCUS) technologies, carbonic acid formed by the dissolution of CO 2 in water induces severe corrosion to steel pipelines, particularly under high temperature (≥90 °C) and the coexistence of oxygen. However, most studies on corrosion inhibitors focus on pure CO 2 environments under mild conditions, while investigations under high-temperature and high-pressure CO 2 /O 2 corrosive environments remain limited. Moreover, O 2 corrosion causes loose and porous products, which exacerbate corrosion, significantly increasing the difficulty of corrosion protection. Therefore, the development of efficient corrosion inhibitors for high-temperature and high-pressure CO 2 /O 2 corrosive environments has become an urgent research priority. In this study, three novel bis-Schiff base corrosion inhibitors containing halogens (-F, -Cl, -Br) were designed and applied in a harsh corrosive environment of 90 °C, 3.5% NaCl solution, 0.5 MPa CO 2 , and 0.08 MPa O 2 . These inhibitors exhibited excellent corrosion inhibition performance on Q235 steel. Furthermore, the most effective bis-Schiff base inhibitor monomer was formulated into a composite system, achieving an inhibition efficiency of approximately 95%. The corrosion inhibition mechanisms were investigated through electrochemical methods and surface characterization, providing new insights into the design of high-efficiency corrosion inhibitors for high-temperature and high-pressure environments.