High temperature corrosion properties of ionic liquids

The corrosion behaviour of several metals and metal alloys (copper, nickel, AISI 1018 steel, brass, Inconel 600) exposed to a typical ionic liquid, the 1-butyl-3-methyl-imidazolium bis-(trifluoromethanesulfonyl) imide, (C₄mim]Tf₂N]), has been investigated by electrochemical and weight-loss methods. Corrosion current densities have been determined by extrapolation from Tafel plots and by polarization resistance measurements and 48 h immersion tests were performed at 150, 250, 275 and 325 °C. Room temperature results show low corrosion current densities (0.1-1.2 μA/cm²) for all the metals and alloys investigated. At 70 °C, the corrosion current for copper dramatically increases showing a strongly dependence on temperature. At 150 °C copper shows significant weight-loss while nickel, AISI 1018, brass and Inconel do not. At higher temperatures (?275 °C), the copper sample crumbles and localized corrosion occurs for the other metals and alloys.