Tribological behavior of environmentally friendly borate ionic liquids with low corrosion degree

ABSTRACT Two novel halogen-free liquids additives [DHB][BScB] and [MA-BIm][BScB] are synthesized and their tribological performance in 500 N base oil are evaluated using 4-ball machine for the first time. The results show that [DHB][BScB] and [MA-BIm][BScB] can decrease the friction coefficient of 500 N base oil by 42.7 % and 42.1 % at 2.5 wt% concentration respectively and they both possess excellent corrosion resistance. According to the analysis results of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), [DHB][BScB] and [MA-BIm][BScB] can form chemical films consisting of iron oxide and B2O3 on the worn steel surface. In addition, a lubrication mechanism is speculated and there may be a competitive adsorption between anion and cation.