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Purpose – The purpose of this paper is to study the antirust, tribological performance and anti-wear (AW) mechanism of the of soybean lecithin (SL) as a kind of multifunctional lubricant additive. Design/methodology/approach – As a kind of multifunctional lubricant additive, the antirust performance of SL was tested according to ASTM D 665, and meanwhile, its tribological performances were also evaluated by Optimol SRV-I oscillating reciprocating friction and wear tester and four ball tester. The worn steel surfaces were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Findings – The results showed that the SL exhibited excellent antirust properties in different base stock, and could effectively improve the AW and extreme pressure (EP) performances. The results of SEM and XPS indicated that a protective film was formed between steel-steel friction pair during the tribological test. Originality/value – This paper first investigated the antirust properties and the tribological mechanism of the SL as a kind of multifunctional lubricant additive, which can be very useful and will promote the application of SL in lubricant industry. [ABSTRACT FROM AUTHOR]

Purpose – To study some tribochemical properties of tetrazole derivatives, n-hexadecanyl (1H-tetrazol-1-yl) acetate (HTA) and 1-phenyl-5-(octylthio)-tetrazole (PCT) as lubricating oil additives in hydrogenised oil, and estimate the action mechanism.Design/methodology/approach – The two tetrazole compounds were synthesized, and added them in hydrogenised oil with different concentrations. Their anti-wear properties were evaluated with a four-ball machine, the wear scar was analyzed with a X-ray photoelectron spectroscopy (XPS).Findings – The novel compounds possess good anti-wear, friction reduction properties and good load-carrying capacity. According to the XPS results, the novel compounds were migrated onto the surface of the steel balls and adsorbed on the surface. The two additive compounds, themselves, and their decomposers contributed to the corresponding tribological performances. With S element contained in the compound PCT, the influence on the load-carrying capacity of the base oil was enhanced. It may be due to the formation of S2- and SO42- compounds on the worn surface which could form a protective film.Research limitations/implications – Their antioxidant, anticorrosion, anti-wear properties are not estimated.Practical implications – Two useful EP and AW lubricating oil additives were synthesized, and maybe it is the potential industrial applied lubricating oil additives.Originality/value – This paper provided a study way of some N-containing heterocyclic compounds as lubricating oil additives. [ABSTRACT FROM AUTHOR]