Tribological behavior of three novel triazine derivatives as additives in rapeseed oil

Three novel phosphorus-free triazine derivatives, referred to as ZOO, ZOS and ZDION, respectively, were synthesized. Their thermal stabilities and anticorrosive properties were investigated. Their tribological behaviors as additives in rapeseed oil were evaluated using four-ball friction and wear testers as well. The results suggest that all the synthesized compounds have good thermal stability, corrosion inhibiting ability and excellent tribological behavior. That is, ZOS has the best extreme pressure, antiwear and friction-reducing properties under a wide range of test conditions. And, ZOO generally possesses excellent load-carrying capacity and good antiwear and friction-reducing abilities. However, ZDION shows poor antiwear effectiveness in rapeseed oil, though it is capable of improving the load-carrying capacity and friction-reducing ability of the base stock under high concentration (>1.5 wt.%) and low load (<392 N). The worn surfaces of the steel balls were observed using a scanning electron microscope coupled with an energy dispersive spectrometer (SEM/EDS) and X-ray photoelectron spectroscope (XPS). It is supposed that the synthetic additives adsorb and react with the steel surfaces during the rubbing process and generate a surface protective film composed of sulfate, sulfide, iron oxide and N- and/or O-containing organic compounds, which accounts for the better tribological behaviors of the base stock containing the synthetic additives as compared with the base stock alone.