Corrosion Behavior of Carbon Steel in CO2 Saturated Amine and Imidazolium-, Ammonium-, and Phosphonium-Based Ionic Liquid Solutions

Abstract

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][BF4], [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 CO2 loading. The findings of the investigation show that corrosivity of classical amines is governed by their characteristic CO2 absorption capacity whereas PZ-activated amines resulted in lower corrosion rates and higher CO2 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. 2015 American Chemical Society.