Single-asperity study of the reaction kinetics of P-based triboreactive films

The reaction kinetics of zinc dialkyldithiophosphate (ZDDP) and ashless DDP antiwear additives were studied using in-situ single asperity AFM experiments. The results show that the ZDDP molecules decompose under high temperature and contact pressure following first order reaction kinetics (n=0.71±0.14), whereas the DDP molecules follow a more complex fractional order (n=0.52±0.07). The fractional order indicates that the decomposition process...