Corrosion of 316L stainless steel in ionic liquid working fluids used for absorption heat pumps or refrigerators

The corrosion behaviour of 316L stainless steel (316L ss) in aqueous solutions of ionic liquid 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]) with different contents of water was investigated by scanning electron microscopy (SEM), potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). The results indicate that 316L in aqueous solutions of ionic liquid [EMIM][DEP] shows an obvious surface passivation, a broad passive region and low corrosion current densities. It also has better corrosion resistivity than in 0⋅177 M LiBr aqueous electrolytes. Furthermore, in order to explain the corrosion mechanism in two working fluids, the Van der Waals volume of ions and the interaction energies of ion pairs were calculated based on the density functional theory (DFT) in quantum chemistry combined with gradient corrected functional using Gaussian 09.