Tribological Performance of Two Potential Environmentally Friendly Ashless Vegetable Oil Additives

Two potential novel environmentally friendly ashless vegetable oil additives, 2-mercaptobenzothiazole derivatives, di-n-dodecyl-[2-(2-benzothiazolyl)thio]ethylborane (LBN) and di-n-dodecylthio-[2-(2-benzothiazolyl) thio]ethylborane (LBNS), were synthesized and their tribological performance as additives in rapeseed oil (RSO) was evaluated using a four-ball wear tester. Their anti-corrosive properties and thermal stability were also examined. The worn surface of the steel ball was analyzed by means of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that 2-mercaptobenzothiazole derivatives exhibited excellent anti-corrosive property and high thermal stability. Moreover, they both had good load-carrying capacities and anti-wear and friction-reducing properties. The PB values of samples decreased in the following order: LBNS> LBN>RSO. The results of XPS examination illustrated that the excellent tribological behavior of the prepared compounds used as additives in RSO was attributed to the formation of a protective lubrication film on the worn surface, which consisted of an adsorption layer and a reaction layer containing Fe3O4, FeS, Fe2(SO4)3, FeB, and organic nitrogen-containing compounds.