A comprehensive study of amino acids based ionic liquids as green lubricants for various contacts

In this paper, a group of quaternary ammonium amino acid ionic liquids (QAAA ILs) prepared by coupling the tetrabutylammonium cation with fourteen types of natural amino acids as base lubricant were investigated for steel/steel, steel/copper and steel/aluminum contacts at ambient temperature and elevated temperature. The corrosion resistance and tribological ability of various QAAA ILs was determined. The influences of various anionic structures on kinematic viscosity , corrosivity , thermal stability and tribological properties of the ILs were discussed in detailed. The copper strip corrosion test results showed that the present ILs have been proved to be almost non-corrosive. Tribological behaviors results displayed that the present ILs exhibit extremely eminent friction reduction and antiwear properties. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis revealed that a protective lubricating film is formed on the surface of contact mainly through a polarity induced physical adsorption when QAAA ILs are selected as neat lubricants, which plays a key role in reducing friction and wear between the moving mechanical interface.