Lubricating Properties of the Protic Ionic Liquids as the Water-Based Lubricating Additives

Protic ionic liquid (Bis(2-hydroxyethyl)ammonium lauric, B_OEAL) aqueous solutions were prepared. Friction-reducing and anti-wear properties, extreme pressure properties, film forming properties and wettability of B_OEAL aqueous solutions were tested on the MRS-10A friction tester, NGY-6 nanometer and Contact angle tester. The friction and wear mechanism were analyzed by 3D surface profiler and X-ray photoelectron spectrometer. The results show that low concentration B_OEAL aqueous solution had excellent extreme pressure performance, and the non-seizure value(P_B)of the B_OEAL aqueous solution(5%) was between 834 N and 883 N. Compared to that of pure water (98 N), the B_OEAL aqueous solution had good extreme pressure performance. The film forming ability of pure water and the wettability of steel-steel friction pair surface were remarkably improved by B_OEAL. The reason was that the polar groups of B_OEAL can form a dense chemical or physical adsorption film on the metal surface, which reduced the friction coefficient and improved the anti-wear properties. Because of the saturated adsorption of the polar molecules, low concentration of B_OEAL aqueous solutions had good tribological properties.