Zinc Dialkyldithiophosphate Additive Adsorption on Carbon Black Particles

Soot is known to cause high wear in engine components and this is a problem with engine oils between extended drain intervals. Although several wear mechanisms have been suggested, exact soot-induced wear mechanisms are still not fully understood. This study aims to investigate the additive adsorption mechanism (specifically anti-wear additive) on carbon black (CB) particles (as a soot surrogate). This mechanism is one of the main mechanisms responsible for high wear. Base oil (BO) was used to exclude the effect of other additives that are present in fully formulated oil. Zinc dialkyldithiophosphate (ZDDP) anti-wear additive was added to the BO and then the mixture, which will be referred to as the model oil, was aged with CB particles. The resulting oils were then chemically characterised by using ICP and FTIR analysis techniques. Finally, the CB particles were filtered out and analysed using EDX. The results showed that both zinc and phosphorous which are chemical elements from ZDDP anti-wear additive were adsorbed on CB particles in the oil phase. This additive adsorption mechanism can lead to increased wear in the engine components due to lack of additives in the oil. This study highlights the importance of understanding the additive adsorption on soot particles since this mechanism will reduce the engine oil life and increase frequency of oil changes.