APPLICATION OF SOFT-X-RAY ABSORPTION-SPECTROSCOPY IN CHEMICAL CHARACTERIZATION OF ANTIWEAR FILMS GENERATED BY ZDDP .2. THE EFFECT OF DETERGENTS AND DISPERSANTS

X-ray absorption near edge structure (XANES) spectroscopy has been use d to study the chemical nature of the antiwear firms generated on stee l surfaces using zinc dialkyldithiophosphates (ZDDPs), in the presence of detergents. and dispersants. The spectra were recorded both in tot al electron yield (TEY) and fluorescence yield (FY) modes, to investig ate the chemical nature of P, S, Ca and O on the surface and in the bu lk, respectively. The interaction of a commercial secondary ZDDP with a calcium sulphonate (neutral) detergent, a calcium phenate (basic) de tergent and a polyisobutylene succinic anhydride polyamide dispersant has been examined. Using a range of concentrations, it has been found that calcium sulphonate interacts with ZDDP only at high concentration (greater than or equal to 2%), whereas calcium phenate affects the fi lm formation even at low concentrations. The strongest interaction has been found for the polyisobutylene succinic anhydride polyamide dispe rsant. The polyphosphate films formed in the presence of the these add itive have shorter chain length compared with ZDDP alone and contain l ess unchanged ZDDP. These finding are discussed in the framework of a mechanism for the film formation presented in Part I of this study. (C ) Elsevier Science S.A.