Comparative Analysis of the Tribological Properties of Hexadecanol and Hexadecanethiol as Lubricating Additives in Synthetic Oils

The improved tribological performance of the lubricating oils addresses durability challenges in mechanical systems. Herein, the physicochemical and tribological properties of 1-hexadecanol (16O) and 1-hexadecanethiol (16S) as oil additives for lubricating steel tribosystems were studied under various concentrations. The tribological behavior of lubricated steel surfaces was evaluated using an SRV-IV tribometer. In addition, a simulation was conducted that highlights the mechanism of additive adsorption on metal surfaces based on density functional theory (DFT). The tribological findings demonstrated that the 16O and 16S additives reduced the friction coefficient by 50-52% and wear volume by 79.9-82.6% compared with PAO10 oil. Notably, the 16O additive offers more consistent and concentration-independent friction reduction, while the 16S additive provides higher anti-wear protection at 0.5 wt% concentration due to the formation of a robust Fe-S tribofilm, which results from its stable physical adsorption mechanism based on simulation results. Briefly, this comparative analysis highlights the importance of optimizing additive concentration based on the specific balance of friction and wear requirements in mechanical applications.