Towards superior lubricity and anticorrosion performances of proton-type ionic liquids additives for water-based lubricating fluids

With the increasingly serious environmental pollution and energy issues, water-based lubricating materials will gradually replace oil-based lubricating materials in some specific applications, which has become a trend. As a water-soluble lubricating additive, the synthesized proton-type ionic liquids (PILs) have the advantages of simple synthesis, good solubility stability, and excellent corrosion resistance properties, providing a method to better solve the problems of traditional water-based additives. The physical-chemical properties and lubrication functions of additives were characterized by foam corrosion test and tribological trials, with the detailed exploration of their lubricating mechanism obtained from QCM, TEM, TOF-SIMS, XPS and MD analysis. The results show that PILs display excellent friction-reducing and anti-wear performances, and improve the carrying capacity for water, which is mainly attributed to the formed tribofilm on the friction surface. The tribofilm is probably triggered by ions pair adsorption on the substrate surfaces, equipping with a typical bilayer structure self-assembly between two convexs. When it worked on the interface, a double layer structure is formed by the way of self-assembly, resulting in the formation of a continuous boundary protective film induced by tribo-chemical reaction, which can effectively reduce the shear damping during friction. Torque testing system results show that PILs have the smaller torque values, indicating their better lubricating performance in the small-scale platform test, which can make it to be used as a potential additive with excellent properties in water-based cutting fluids.