Surface analytical studies of surface-additive interactions, by means of in situ and combinatorial approaches

The influence of tribological conditions on the surface reactions occurring between zinc dialkyldithiophosphate (ZnDTP) and steel surfaces has been studied by means of a combination of X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), in situ attenuated total reflection (ATR) infrared spectroscopy, and high-throughput combinatorial approaches. Purely thermal treatment at 150 °C appears to lead to the formation of zinc polyphosphates. However, in the presence of tribological stress, simple phosphates appear to dominate, with some indication that higher load conditions lead to an increase in the surface concentration of both phosphate and, at higher temperatures, polyphosphate.