A High-Performance Multifunctional Lubricant Additive for Water–Glycol Hydraulic Fluid

Abstract

A water-soluble boron (B)-containing thiophosphite derivative (BTP) was synthesized, and its tribological, anticorrosion, and antirust properties as an additive for the base liquid of water–glycol hydraulic fluid were evaluated in detail. The results of tests demonstrated that BTP is indeed a high-performance and multifunctional water-soluble lubricant additive that was able to remarkably improve the extreme pressure, friction-reducing, antiwear, anticorrosion, and rust-inhibiting properties of the base liquid when added at a low adding concentration (<3 wt%). Based on a performance comparison of BTP and thiophosphite (TP), whose chemical structure is similar to that of BTP but without B, a number of primary conclusions were drawn. The B element existing as alkanolamine borate group could greatly improve the extreme pressure, antiwear, and antirust performance of BTP, especially the antirust performance, but had only a small effect on the friction-reducing and anticorrosion properties. Based on characterizations and analyses of the worn surfaces, we propose that the antiwear mechanism consists of the prepared compound BTP reacting with the steel surface during the friction process to generate a protective film mainly composed of phosphate, sulfide, sulfate, organic amine, and B2O3.