Extreme pressure and anti-wear mechanism of two P, N-containing additives

A phosphate amine salt and a phosphonic amine salt were synthesized. The load-carrying capacity, antiwear, friction-reducing, anticorrosion and antirust behaviors of the synthetic products as additives in liquid paraffin and a commercial mineral oil 500 SN were investigated. The antiwear and friction-reducing properties of the synthetic additives were compared with that of sulphurized olefin (SO), zinc dialkyldithiophosphate (ZDDP) and dibutyl phosphate (DBP). The elemental composition and chemical states of the wear scar on the SAE 52100 steel ball were examined by means of X- ray photoelectron spectroscopy (XPS). The results show that phosphate amine salt and phosphonic amine salt additives have much better extreme pressure properties than the conventional S, P and/or Cl-containing additives. XPS analysis of the wear scar indicates that PN agents function to reduce friction and wear mainly by forming tribochemical reaction film on lubricated steel surface, which is accompanied by adsorption of the additives on the steel surface.