A Tribological and Electrochemical Study of Protic Ionic Liquid and Bentonite Particles Used as Lubricating Additives in Water-Based Lubricants

The objective of this work is to evaluate the wear and corrosion behaviours of different formulations of water-based lubricants containing protic ionic liquid (PIL) and bentonite particle additions. Carbon-steel samples were investigated in the normalized and quenched-tempered conditions. Wear tests and corrosion tests using potentiondynamic polarization curves were performed in the presence of different lubricant solutions (PIL 3 wt% + deionized water, with 0.05 wt% and 0.1 wt% bentonite particle additions). Wear scar surfaces were analysed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Raman techniques. Unexpected electrochemical effects caused by the bentonite addition promoted the formation of a thick oxide film (Fe 3 O 4 ) in the quenched-tempered steel during the wear test, which mitigated the wear in the presence of a minimum amount of this particle in the formulation.