Molecular simulations of amine-based organic additives at a steel surface: Effect of the internal molecular structure on adsorption

Abstract

Lubricating oils mitigate wear in gears and rolling bearings lengthening the lifespan of drivetrain units for electric vehicles. Amine-based organic additives from the lubricating oil contribute to alleviating wear by adsorbing on rubbing steel surfaces of mechanical contacts and forming anti-wear films. Cross-pin wear experiments suggest that additives with branches in polar heads improve wear protection, while remaining environmentally friendly. Experiments show a reasonable correlation with the energy of adsorption calculated from molecular dynamics simulations at large surface coverages. Whereas adsorption strengths and surface coverages are barely affected by the conformation of alkyl chains (cis/trans), they are affected by the length of branches in polar heads of additives. Results suggest better performances for branch lengths containing 3–4 C atoms.