Tribological study of OH- and N-containing imidazoline derivatives as additives in water-glycol

Tribological properties of two hydroxyl- and only active nitrogen-containing water-soluble imidazoline derivatives, benzotriazole-containing imidazoline (BML) and caprylic acid-containing imidazoline (CML), as lubrication additive in water-glycol hydraulic fluid were evaluated with a four-ball tester. And the antirust and anticorrosion behaviors were also investigated. Results show that BML and CML were able to remarkably improve the antirust properties of water-glycol fluid when added at a low adding concentration, and also these performances of BML was better than CML. All additives exhibited good extreme pressure and antiwear properties, and BML showed better tribological properties than CML. Besides, the difference in the tribological and anticorrosion properties of these derivatives was closely related to their different molecular structures. There exists a synergistic tribological effect between benzotriazole and imidazoline group in the tribological and antiwear performances. Furthermore, significant improvement in the tribological performances of BML was detected and attributed to organic nitrogen compounds, iron oxide, and so on in tribofilm on the worn surfaces.