Protic Ionic Liquid Additives Achieving Multifunctional Integration of Superior Lubricity, Corrosion Resistance, and Biodegradability

Three green amino acid-based ionic liquids (AAILs) were synthesized, and their tribological properties, corrosion inhibition capabilities, and biodegradability as water-based additives were systematically evaluated. The addition of 1 wt % of AAILs significantly enhanced the lubrication performance and corrosion resistance of water, of which triisopropanolamine-lauroyl glutamic acid (TIPA-LG) exhibited the most outstanding tribological properties. Compared to water, the coefficient of friction (COF) and wear volume (WV) of TIPA-LG were reduced by 68.5 and 95.5%, respectively. TIPA-LG can form a physical and chemical adsorption film and a friction chemical reaction film at the friction interface. The synergistic effect of these two lubrication films effectively reduces the direct contact between metal surfaces, thereby enhancing the friction-reducing and antiwear properties of the lubricant. Furthermore, TIPA-LG demonstrated excellent environmental compatibility, achieving a biodegradation rate of 80.89% within 28 days. These environmentally friendly, high-performance, water-based lubricant additives show promise in metal working applications.