A corrosion-resistant green ionic liquid achieves near-zero wear at the interface with engineering steel

Abstract

The development of high-performance, environmentally friendly lubricants has attracted widespread attention in the lubrication field. However, achieving ultra-low wear at the steel/steel interface remains a significant challenge. In this study, several green ionic liquids (ILs) were synthesized based on 1,1,3,3-tetramethylguanidine (TMG), achieving virtually no wear on the steel surface, with a wear rate of 2.26 × 10⁻¹⁰ mm³ N⁻¹ m⁻¹, representing a 99.8% reduction compared to the conventional green lubricant PEG (1.22 × 10⁻⁷ mm³ N⁻¹ m⁻¹). After a 3-hour friction test at a contact pressure of 2.15 GPa, the steel surface still exhibited ultra-low wear, with a wear rate of only 9.95 × 10⁻¹¹ mm³ N⁻¹ m⁻¹. Compared to existing studies, this work has brought research on near-zero wear at steel interfaces to the 10⁻¹¹ order of magnitude, demonstrating excellent tribological performance. Furthermore, electrochemical and copper corrosion protection tests revealed that ILs exhibit exceptional corrosion-inhibiting properties on the surfaces of Cu, Fe, Al, and Zn metals. Mechanistic studies found that the synergistic interaction of the adsorption film, frictional chemical film, and hydrodynamic lubrication mechanisms during the friction process provides long-lasting and highly effective protection for the steel surface. Additionally, the environmental compatibility and acute toxicity of this lubricant were evaluated through mung bean germination and antibacterial experiments. This study provides a new design approach for green lubricants to achieve near-zero wear in engineering steels.