Protic ammonium carboxylate ionic liquid lubricants of OFHC copper

The protic ionic liquids (PILs) di-[bis(2-hydroxyethyl)ammonium] adipate (DAd), bis(2-hydroxyethyl)ammonium salicylate (DSa) and bis(2-hydroxyethyl)ammonium oleate (DO), composed of organic anions and cations, were selected for pin-on-disc tribological tests as lubricants of OFHC copper discs sliding against OFHC copper pins, after corrosion tests. The tribological performance of the new PILs was compared with that of the non-polar synthetic lubricant PAO 6 and with the aprotic ionic liquid (APIL) 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM](CF3SO2)2N). The order of coefficients of friction and wear rates was: DAd