Adsorption of ionic liquid additives for water-based lubrication

Water-based lubricants have the advantages of high thermal conductivity, good cooling performance and low pollution. However, they often suffer from poor dispersion and dissolution stability, low reactivity and high corrosiveness. Ionic liquids (ILs) can overcome some of these drawbacks. In addition, they have been developed as a new additive with good friction-reducing and anti-wear functions. It is widely hypothesized that the tribological properties of these ILs arise from the nanostructure of their adsorbed layer on the steel surface through self-assembly, but the exact structural details of the IL molecules remain elusive. It has also been hypothesized that these ILs could form a sandwiched bilayer on the metal surface with the hydrophobic tails packed in the middle and hydrophilic head groups pointed outside. However, how the nanostructures determine the tribological properties of these ILs remains inconclusive.