Study of the effects of Ca sulfonate on antiwear film formation by X-ray absorption spectroscopy using synchrotron radiation.
All additives and model compounds used in this study were commercial products: a sec-ZDDP, Calcium sulfonate (neutral) and calcium sulfonate (overbased, 400 TBN). Total Base Number (TBN) is a measure of the alkalinity of an additive and is equivalent to mg of KOH per a gram of additive. All the additives were supplied in a concentrated form in oil. The additive concentrates were diluted in MCT-10 base oil in the following concentrations: sec-ZDDP, 1.2 wt.%; detergents, 2 and 6 wt.%. The antiwear films were generated on 52100 steel coupons. Prior to film generation, the 52100 steel coupons were polished using 3 lain diamond paste. The coupons and cylindrical pins were cleaned m an ultrasonic bath using a light hydrocarbon solvent (hexane). The antiwear films were prepared using a Hint reciprocating wear tester. Data acquisition and data analysis have been described elsewhere [Ym et al., 1997a].