Abstract: X-ray absorption near-edge structure (XANES) spectrum of thermal and tribochemical films of alkyl polysulfides with different sulfur contents was determined. It was found that the chemical nature of these films was strongly dependent on the operating environment for the additives. That was, the thermal films of the serial polysulfides were composed of FeSO4 or Fe2(SO4)3 under 70 ℃ and 150 ℃, the thickness of thermal films increased with the increasing of the temperature and additives′ sulfur content. Tribochemical films were composed of different forms of sulfur rather than iron sulfate observed in the thermo-oxidative films. They were mixtures of iron sulfate, pyrite and sulfoxide, and the rise of sulfur content led to the increase of thickness in the tribochemical films.

Key words: Alkyl polysulfide, XANES, Tribochemical film, Thermal film