Abstract: The friction and wear properties of an Al2024 alloy against AISI52100 steel were evaluated on an Optimol SRV friction and wear tester. The friction and wear tests were carried out under the lubrication of liquid paraffin alone and liquid paraffin containing various extreme pressure and antiwear additives. The additives including tricresyl phosphate (TCP), dibutyl phosphite (DBP), dodecylamine (DA) and a phosphated amine salt (PAS) were used. The boundary film formed on the rubbed surface of Al2024 was analyzed with a scanning electron microscope (SEM) and X ray photoelectron spectroscope (XPS). As the results, P containing additives such as TCP and DBP in liquid paraffin significantly increase the anti wear ability and reduce the friction coefficient. PAS in liquid paraffin shows the best anti wear and friction reducing properties. The improvement in the antiwear and friction reduction behavior of the Al steel pair is attributed to the formation of the boundary film composed of aluminum phosphate and/or aluminum phosphite on the lubricated surfaces.