The chemistry, mechanism and function of tricresyl phosphate (TCP) as an anti‐wear lubricant additive

Abstract

AbstractThe detailed understanding of the physical and reaction chemistry of engineering lubricants is key to new developments in the future. Here, we draw together the main chemical/engineering literature in the first systematic review of the standard anti‐wear additive used as an aviation lubricant, tricresyl phosphate (TCP), focusing on understanding the links between the surface chemistry, tribology and decomposition of TCP. While there is still debate concerning the mechanism of TCP, it is clear that it is activated by moisture, oxygen or oxidised metal surfaces. Its anti‐wear properties arise from the resulting formation of iron phosphate or polyphosphate on the contact surfaces. Evidence stresses the importance of chemistry at the boundary layer and a mechanism involving pre‐coordination of TCP at the surface, resulting in activation at the P‐centre and subsequent attack by residual H2O or surface O2−. This perspective provides a potential baseline for the development of future phosphorus‐based high‐performance additives. Copyright © 2015 John Wiley & Sons, Ltd.