Synthesis of a Novel Multifunctional Ionic Liquid Based on Benzotriazole for Enhanced Tribological Performance of Steel Interfaces

Abstract

A novel oil-soluble ionic liquid (ILs), benzotriazole-functionalized quaternary phosphonium salt (BTAP₈₈₈DOSS), has been synthesized. This proposed oil formulation incorporates the BTAP₈₈₈DOSS additive into poly-α-olefin (PAO10) oil. The tribological, corrosion, and thermal properties were investigated. The wear patterns and tribofilm formation mechanisms for the formulated lubricant are discussed using advanced technologies (SEM, XPS, and TOF–SIMS). Moreover, the molecular models of cations and anions were generated and optimized using density functional theory (DFT). Notably, the oil prepared with 0.5 wt% BTAP₈₈₈DOSS additive exhibited superior lubrication performance, minimizing the friction coefficient by 34–36% and disc wear volume by 80–85% compared with the baseline lubricant. This reinforcement is attributed to the additive’s ability to form a lubricating layer with low shear forces, as demonstrated by the simulation results. Ultimately, our results will support the advancement of eco-friendly ILs as multifunctional oil additives to reduce power losses caused by friction in various mechanical systems.