Understanding the corrosion behavior of carbon steel in amino-functionalized ionic liquids for CO2 capture assisted by weight loss and electrochemical techniques

Abstract

One of the main challenges in post-combustion CO2 capture with chemical absorbents is equipment corrosion, which contradicted the requirements of green economy and sustainable development. As novel solvents for CO2 capture, amino-functionalized ionic liquids (AFILs) have attracted wide attentions in recent years. Nevertheless, equipment corrosion of CO2 capture into AFILs solution is still rarely studied. In the present work, corrosion behavior of 20# carbon steel in five AFILs solutions ([N1111][Gly], [AEMIm][Gly], [AEMIm][Lys], [DETAH][Lys], [TETAH][Lys]) were evaluated by weight loss methods, Tafel curve and electrochemical impedance spectroscopy (EIS). The experimental results indicated that all of the fresh AFILs solutions showed a negligible corrosivity, while the CO2-loaded solutions presented high corrosivity on carbon steel. The corrosion was accelerated as the amount of amino-functionalized group in AFILs increased. Moreover, the carbon steel before and after corrosion were analyzed by SEM, EDS, XRD. The characterization analysis showed that there was only Fe, but no protective layer of FeCO3 presented on the surface of 20# carbon steel, which was different with that of amine solutions in the reported works. On the basis of the experimental data and characterization analysis, the corrosion mechanism of carbon steel in AFILs system was proposed. The corrosion process was controlled by charge transfer. In the fresh AFILs solutions, there were no cathodic substances (HCO3−, H+) to promote the dissolution of iron. In CO2-saturated AFILs solutions, CO2 was absorbed to form HCO3−/CO32− and carbamates, which fasted the rapid dissolution of iron on carbon steel surface and promoted the corrosion.