Enhancing the tribological performance of PEG 200 using oil-miscible deep eutectic solvents as lubricant additives

Abstract

This study investigated a comprehensive assessment of the tribological and anti-corrosion behavior of a novel, halogen-free, and oil-miscible deep eutectic solvent (DES) additive in PEG 200. The DES, referred to as DOA, was synthesized from naturally derived L-Proline and oxalic acid and exhibited good miscibility with PEG 200 due to its polar functional groups. Corrosion tests, including electrochemical and copper strip experiments, confirmed that the DOA/PEG blends maintained consistent anti-corrosion performance. Tribological evaluations revealed that incorporating 3 wt% DOA resulted in a 30 % reduction in the coefficient of friction and a 60.3 % decrease in wear volume compared to PEG 200 alone. ANOVA analysis validated the statistical significance (p < 0.05) of DOA concentration on friction and wear responses, confirming a synergistic effect between DOA and PEG 200. These improvements are attributed to strong interfacial interactions and the formation of a protective tribo-chemical film. Surface characterization identified the presence of hydrocarbons (CxHy), iron oxides, and FeOOH layers, which improved lubrication in the steel–steel contact pair. These findings highlight the potential of DOA as a promising green additive for advancing sustainable lubrication technologies. © 2025 Elsevier Ltd