ZDDPs anti-wear mechanism

The volatile components from ZDDPs may also arise from thermal degradation and/or oxidation. The mechanisms proposed for ZDDP anti-wear and anti-oxidation performance in motor oil have included both the effects of ZDDP degradation and oxidation [2], In addition, P NMR studies at other laboratories have identified ZDDP breakdown fragments in the used motor oil [12], as shown in... 

There is some correlation between the work presented here and other work carried out to investigate the effect of calcium detergents on the anti-wear mechanism of ZDDP [9, 19, and 20]. The study by Wan et al. [20] has shown that there is an antagonistic effect between the detergent and the anti-wear additives which can reduce the effectiveness of the anti-wear properties of ZDDP. This effect occurs by the breakdown of calcium carbonate containing colloids and the deposition of Ca-soap molecules on the surface. 

ZDDP (zinc dialkyl dithiophos-phate or zinc diaryl dithiophos-phate)—widely used as an anti-wear agent in motor oils to protect heavily loaded parts, particularly the valve train mechanisms (such as the camshaft and cam followers) from excessive wear. It is also used as an anti-wear agent in hydraulic fluids and certain other products. ZDDP is also an effective oxidation inhibitor. Oils containing ZDDP should not be used in engines that employ silver alloy bearings. All car manufacturers now recommend the use of dialkyl ZDDP in motor oils for passenger car service. 

The anti-wear performance of the additive packages is often insured by ZDDP additive. How ZDDP additives form protective films on rubbing surfaces has been a concern for researchers in the field of tribology since the performance of the additive was first reported. The mechanism of wear film formation is important for two reasons - firstly to understand how current additives function and hence determine the limits of their usefulness and... 

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