Study on Carbon Steel Corrosion in Mixed Amine Absorbents for CO 2 Capture

To address the severe corrosion caused by 30% monoethanolamine (MEA) in carbon capture, this study developed mixed amine absorbents (30 wt % total) by combining MEA with 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ), N -methyldiethanolamine (MDEA), 2-(2-aminoethylamino)ethanol (AEEA), or diethylenetriamine (DETA). The corrosion behavior on 20# carbon steel was evaluated through novel dynamic immersion tests, electrochemical analysis, and multitechnique characterization. Results revealed the corrosion rate order as 20% DETA + 10% MEA ≫ 20% AEEA + 10% MEA > 30%MEA > 20% MEA + 10% PZ/AMP/MDEA > 20% PZ/AMP/MDEA + 10% MEA. AMP, MDEA, and PZ promoted protective FeCO 3 film formation via HCO 3 – generation, whereas AEEA and DETA intensified corrosion, forming nonprotective green rust (Fe 6 (OH) 12 CO 3 ·2H 2 O). The work further clarifies the competitive regulatory mechanism of degradation products─corrosion-accelerating heat-stable salts (e.g., formate) and corrosion-inhibiting degradation product N -hydroxyethyl-2-imidazolidinone (HEIA). The absorption–degradation–corrosion interrelationship was systematically elucidated. These findings provide a mechanistic basis for designing efficient, low-corrosion amine solvents for carbon capture.