Effect of electric field on lubricating film thickness of ionic liquids in tribological applications

Abstract

In this work, the effect of an external electric field on the thickness of the lubricating film is investigated using optical interferometry in the “ball-on-disk” configuration. The synthetic oil R 825/95 was used as a reference and compared with the ionic liquid 1-hexyl-3-methylimidazolium chloride (HMIMCl). The results show that the oil exhibits no response to the electric field, while HMIMCl showed a strong dependence on the electric voltage and polarization conditions. The total duration of the measurement was 900 s, during which the initial growth phase in the first 500 s by was followed by saturation and stabilization of the film thickness. This behavior is attributed to ionic reorganization and the formation of ionic layers. Under anodic polarization, the layer thickness increased sharply by 48 %, while under cathodic polarization it decreased very negligibly. These results confirm the potential of ionic liquids to be used as lubricants or lubricant additives, enhancing lubrication performance and thereby extending service life and reducing failure rates in mechanical systems with moving parts requiring lubrication.