Volatile degradation products of zinc dialkyldithiophosphate (ZDDP) composed of phosphorus and sulfur compounds reduce the efficiency of catalytic converters resulting in harmful emissions. A unique way of reducing ZDDP level while maintaining good antiwear performance has been achieved by introduction of a novel additive FeF3 along with ZDDP. The interactions between FeF3 and ZDDP are strong enough not only in overshadowing the undesired interactions between ZDDP and additive package but result in more ‘protective film’ than the usual tribo-film from ZDDP decomposition products. The objective of this research is to examine the chemical interactions between ZDDP and FeF3 underlying the improved wear performance. The approach adopted involves thermal degradation of ZDDP that helps in understanding the underlying mechanism in terms of the products that are formed in presence and absence of FeF3. Nuclear Magnetic Resonance Spectroscopy (31P and 19F) has been principally used to identify these products. Results have indicated the formation of new fluorinated phosphorus compounds formed as ‘early intermediate’ products in the reaction between ZDDP and FeF3. The chemical differences observed were used to justify the improved tribological behavior of the new fluorinated ZDDP compounds in comparison to ZDDP.

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