The use of alkanolamines is regarded as the most commonly used way in carbon capture and storage system (CCS) for carbon dioxide capture due to their best comprehensive effect compared with other methods. This work investigated the effect of monoethanolamine (MEA), diethanolamine (DEA) and N-methyldiethanolamine (MDEA) on the corrosion behavior of N80 steel in water-saturated supercritical
CO2 phase and supercritical CO2-saturated aqueous phase with impurities (SO2, NO2 and O2). The
results by weight-loss measurements showed that all the tested alkanolamines inhibited corrosion, and the inhibition efficiency of the three alkanolamines at a concentration of 300 ppmv was between 55% and 67% in the aqueous phase, whereas the inhibition efficiencies were low in the water-saturated supercritical CO2 phase. The off-line pH measurements indicated that alkanolamines could increase the pH value of the solution. Scanning electron microscopy (SEM) was employed to investigate the surface morphology of the corroded specimens after corrosion for 24 h, and 3-dimensional profilometer was applied to measure the pitting rate of specimens after the removal of corrosion products. Chemical and phase compositions of corrosion products were tested by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively.
Key words: CCS, alkanolamine, supercritical CO2, impurity, inhibition efficiency