Evaluating tribological properties of the stearic acid-based organic nanomaterials as additives for aqueous lubricants

Lubricant additives can effectively enhance tribological properties of water, but most of them are environmentally hazardous. Based on the solubilization principle of surfactants, the water-insoluble stearic acid (SA) can be dissolved in the sodium dodecylbenzene sulfonate (SDBS) aqueous solution to form a milky white liquid (SSA aqueous solutions). This paper presents an evaluation of tribological properties of SSA solution. Compared with the pure water, the SSA aqueous solution is more effective in reducing the friction and wear of the friction pairs. The enhancements are due to the following aspects: (1) on the surfaces of the metals, the SSA aqueous solution can be spread out more easily to form liquid lubricant films; (2) the adsorbed SDBS films can inhibit the corrosion behaviors of the metals; (3) the continuous SSA films can separate the direct rubbing between the friction pairs. The SSA solutions show promising results in reducing friction and wear for various friction pairs under a range of loads and shearing velocities, and can be used as potential lubricants in various processes.