Effect of cation nature on the lubricating and physicochemical properties of three ionic liquids

In this work, the lubricating ability and physicochemical properties of three ionic liquids (ILs) containing the same anion and three different cations are studied. Steel-steel contact, lubricated with each IL was studied using a ball-on-flat reciprocating tribometer. The three ILs presented very similar values of thermal stability, density, and surface tension. Trihexyltetradecylammonium bis(trifluoromethylsulfonyl) amide showed the best wettability at 25 °C, but the worst wettability at 100 °C. The influence of the surface finish in the lubricating properties of the ILs were also investigated. Results show higher wear values for fine-finished surfaces. No significant differences in the tribological performance of the ILs are found at low frequency; however, tribo-attack of the imidazolium-based IL on steel, resulted in higher wear at 5 Hz.