Study of the effects of Ca sulfonate on antiwear film formation by X-ray absorption spectroscopy using synchrotron radiation

X-ray absorption near edge (XANES) spectroscopy at the P and S L-edge and K edges has been used to characterize antiwear films generated from combinati ons of the antiwear additives, zinc dialkyl dithiophosphates (ZDDPs), and t he detergent additives, Ca sulfonates. The results clearly show the interac tion of the detergent with the ZDDP in antiwear film formation. Zinc polyph osphate, in part, is converted to calcium phosphate. There are substantial differences between the effect of the neutral and overbased detergents. Wea r is also affected by the presence of the detergent.