Effect of water content on the corrosiveness of imidazolium-based ionic liquids

Ionic liquids (ILs) are gaining attention in CO2 absorption, thanks to their favorable selectivity towards CO2 and physical characteristics, yet their corrosion behavior towards metallic equipment needs deeper evaluation, especially when approaching potential working conditions. Here we investigate the behavior of carbon steel and stainless steel in imidazolium based ILs with different alkyl chain lengths, mixed with various water contents. Oxygen reduction is identified as cathodic process, with limiting current density affected by fluid viscosity, oxygen solubility and diffusivity. The effect of water on ILs corrosiveness changes with its quantity and depends on the formation of a miscible solution or phase separation. Moreover, dissociation of ILs anions releases fluoride ions in water phase, increasing electrolyte aggressiveness.