Study on Corrosion Characteristics of Q235B Carbon Steel in Mixed Amine Absorbents

Against the global carbon neutrality backdrop, amine-based CO2 capture technology is critical for industrial greenhouse gas emission reduction. However, mixed amine absorbents can cause severe corrosion of Q235B carbon steel, restricting the stable operation of carbon capture, utilization, and storage (CCUS) projects. This study systematically investigated the corrosion behavior of Q235B carbon steel in a novel mixed amine system under simulated industrial conditions using weight loss tests, electrochemical measurements (EIS, potentiodynamic polarization), and advanced characterizations (FT-IR, 13C NMR, SEM-EDS, XRD). The temperature was the dominant factor: corrosion rate increased significantly with rising temperature. Under CO2-saturated conditions, 15–30% absorbent concentrations showed no significant effect on corrosion rate owing to similar molar loading and pH. At 60 °C and 30% concentration, the corrosion rate peaked at 30 L/L CO2 loading. Carbamate accumulation promoted corrosion at low loading, while increased bicarbonate inhibited corrosion at high loading. The main corrosion products (Fe3O4, Fe2O3) formed loose, porous films with poor protectiveness. This work clarifies the electrochemical corrosion mechanism and provides data support for corrosion prevention in CCUS equipment.