Study on Lubrication Behaviors of the Overbased Ca Sulfonate with ZDDP 2004-01-3052

The synergic effect between overbased calcium sulfonate detergent (OBCaSu) and zinc dialkyl dithiophosphate (ZDDP) on antiwear property was investigated. The wear test was conducted on a four-ball wear tester. The protective film formed on the worn steel surfaces was examined using scanning electron microscope (SEM), energy dispersive spectroscope (EDS) and X-ray photoelectron spectrometer (XPS). Wear test shows that there is significantly synergic effect between OBCaSu and ZDDP on antiwear property, and the optimum OBCaSu/ZDDP weight ratio can be found. Surface analyses indicate that this synergic effect derives from the formation of protective film generated by the interaction between OBCaSu and ZDDP. During friction process, ZDDP reacts with calcium carbonate in OBCaSu with the generation of calcium phosphates, which possesses good antiwear characteristic.