Effect of amines on the antiwear properties of P‐containing compounds as oil additives

This paper reports a study on the effects of concentration and the molecular structure of amines on the antiwear properties of TBP, TCP and TBPi, evaluated with a four‐ball machine. It was found that amines reduce the antiwear properties of P‐containing additives in the order primary>secondary>tertiary amine, and a critical amine concentration exists at which P‐containing additives lose their antiwear properties. XPS analysis indicated that the competitive adsorption of amines onto the rubbed surface causes a reduction of the antiwear properties of P‐containing additives.