Compatibility of Imidazolium-Based Ionic Liquids for CO2 Capture with Steel Alloys: a Corrosion Perspective

Ionic Liquids (ILs) could find applications in CO2 stripping, where their use could reduce energy consumptions compared to current technologies based on amine absorption. Although preliminary studies showed potential compatibility between metallic alloys and a limited number ILs, their corrosiveness still needs to be fully assessed. This work analyzes the corrosion behavior of steel alloys in contact with several imidazolium-based ILs, changing alternatively cation and anion to highlight possible dependences of corrosion behavior on relevant groups. Potentiodynamic polarization tests were performed in all ILs considered and in water as reference. Different ILs preparation conditions were considered: after purging in nitrogen, i.e., with reduced content of oxygen and water, and after exposure to the atmosphere to restore their natural humidity and oxygen content. Results showed a reduction in the protective character of stainless steel passive film, with no clear trend related to anion composition or cation chain length. Conversely, carbon steel corrosion rate decreased compared to aqueous solutions, and a passivation effect was observed in presence of long chain cations, which was ascribed to a steric effect of adsorbed molecules. (C) 2016 Elsevier Ltd. All rights reserved.