Corrosion Behavior of Carbon Steel in CO2Saturated Amine and Imidazolium-, Ammonium-, and Phosphonium-Based Ionic Liquid Solutions

This work presents a recent investigation on corrosion behavior of carbon steel amine and ionic liquid based carbon dioxide absorbents. The first class focused on classical amine solutions: monoethanolamine (MEA), diethanolamine, and methyldiethanolamine. The second class included activated amine blends using piperazine (PZ) amine promoter. The third class included novel aqueous mixtures of alkanolamine/hydrophilic room-temperature ionic liquids (RTILs), namely, [BMIM][BF 4 ], [BMIM][Otf], [P4441][Acetate], and [Choline][Acetate]. Electrochemical corrosion experiments were conducted using polarization techniques to determine the corrosion rate of steel probing the effect of process temperature and CO 2 loading. The findings of the investigation show that corrosivity of classical amines is governed by their characteristic CO 2 absorption capacity whereas PZ-activated amines resulted in lower corrosion rates and higher CO 2 absorption. The partial replacement of aqueous phase in MEA solution by RTILs was shown to be effective in reducing steel corrosion rates with phosphonium- and ammonium-based RTILs shown to be more effective than imidazolium-based RTILs.