Study of tribological performance and mechanism of phosphonate ionic liquids for steel/aluminum contact

Three kinds of phosphonate ionic liquids (PILs), 1-butyl-3-methylimidazolium O-butyl phosphonate (BMIM-BP), 1-butylpyridinium O-butyl phosphonate (BPy-BP) and N, N-dibutylammonium O-butyl phosphonate (TBA-BP) were synthesized and evaluated as lubricants for steel/aluminum contact. Results show PILs perform much better lubricating properties than conventional ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and liquid paraffin, although the wear volume of BMIM-BP is larger than that of liquid paraffin. The results of corrosion tests of the PILs demonstrate that the lubricating properties of PILs are relevant with their electrochemical properties. Moreover, the tribological mechanism was discussed by surface characterizations and contrastive experiment. It is concluded that the tribological performances of the PILs are related to the formation of the ordered adsorption films, tribochemical reactions and their corrosion properties.