Corrosion Behavior and Mechanisms of Carbon Steel in the 1,4-Butanediamine/Ethylene Glycol/H2O CO2 Capture System

The chemical absorption of CO2 using amine aqueous solutions is the most well-established and efficient approach to CCUS technology. However, these solutions can corrode carbon steel infrastructure, impacting production safety and cost-effectiveness. This study identifies a high CO2 loading (1.2561 mol mol–1) ternary system of 1,4-butanediamine (BDA), ethylene glycol (EG), and 70 wt % H2O (BE70H). The corrosion behavior and mechanism of BE70H on 20# carbon steel (20CS) were studied by weight loss test, ICP-OES analysis, electrochemical experiment, and various characterization techniques, with 30 wt % MEA solution was selected as a reference. The results show that the CO2-loaded amine solution is more corrosive to 20CS than the fresh solution. Fresh and CO2-saturated BE70H solutions (BE70HS) exhibited lower corrosion rates and lower iron concentrations. The characterization results showed that the surface of 20CS corroded by BE70HS formed a dense siderite (FeCO3) film. This film is believed to provide better corrosion inhibition than the chukanovite (Fe2CO3(OH)2) film formed in MEA-saturated solutions. The quantum chemical parameters, such as EHOMO, ELUMO, and ΔE, indicate that BDA molecules exhibit stronger adsorption on the surface of 20CS compared to MEA, effectively inhibiting the penetration of corrosive agents. The FeCO3 film and the adsorbed BDA layer on the 20CS surface are considered the major and minor pathways of corrosion inhibition, respectively. Furthermore, the phase separation behavior of the BE70H solution can potentially lead to differences in corrosiveness, making it a critical factor to consider in equipment anticorrosion design.