Anticorrosion imidazolium ionic liquids as the additive in poly(ethylene glycol) for steel/Cu-Sn alloy contacts

3-((1H-benzo[d][1,2,3]triazol-1-yl)methyl)-1-methyl-1H-imidazolium hexafluorophosphates ([BTAMIM][PF ₆]) ionic liquids (ILs) were evaluated as friction reduction, antiwear (AW) and anticorrosion additives in poly(ethylene glycol) (PEG) for steel/Cu-Sn alloy contacts at 100 °C. The physical properties of PEG with the additive were measured. The anticorrosion properties of [BTAMIM][PF ₆] was assessed via the accelerated corrosion test, which reveals the excellent anticorrosion properties in comparison with selected conventional ILs that have no benzotriazole group. Tribological results indicated that [BTAMIM][PF ₆] as additives could effectively reduce the friction and wear of sliding pairs in PEG. The tribological properties were generally better than the normally used dibutyl phosphite (T304) and conventional ILs L-P108 in PEG. The wear mechanisms are tentatively discussed according to the morphology observation of worn surfaces of Cu-Sn alloy discs by scanning electron microscopy (SEM) and surface composition analysis by X-ray photoelectron spectroscopy (XPS), which revealed complex tribochemical reactions during the sliding process leading to a surface protective film composed of [Cu(-C6H5N3-R)], Cu ₂O, CuF ₂ and C-O bond containing compound is formed. A strong interaction between benzotriazole and the surface of the Cu alloy was proposed to account for the excellent friction reduction, anti-wear and anti-corrosion capability improvement.