Enhanced tribological and corrosion performance of lubricants using eco-engineered LDH-based hybrid additives

An eco-friendly biomass-containing LDH-based hybrid additive was developed using three different LDH materials: Ni/Al-LDH, borate-LDH, and phosphate-LDH. The individual additives Ni/Al-LDH (LDH), borate-LDH (B), phosphate-LDH (P), and biomass additive (Q) were evaluated for corrosion protection and tribological performance on API 5L X70 steel. Tribological testing demonstrated substantial reduction in coefficient of friction, decreasing from approximately 0.20 to 0.03 with LDH-P-B-Q under boundary lubrication conditions. Electrochemical studies conducted according to ASTM G199-09 and ASTM G185 standards revealed excellent corrosion protection, with nearly 97% reduction in corrosion rate and decrease in fluid-flow corrosion from 75 × 10−6 to 23 × 10−7 mm·year−1. Rheological analysis showed that the additive-containing lubricant possessed higher viscosity (213-235 mPa·s) compared to the base oil (190 mPa·s), promoting stronger lubricating film formation, enhanced load-carrying capacity, and reduced surface wear. The lubricant exhibited near-Newtonian flow behavior according to the Ostwald-de Waele model, indicating stable flow characteristics across varying shear conditions. XRD and FESEM confirmed the robust layered architecture of LDH-P-B-Q. Although all formulations displayed similar contact angles, the higher viscosity of LDH-P-B-Q enabled superior surface separation and load-bearing capability under boundary lubrication. The biomass component is believed to contribute to thermal stability and viscosity retention through its carbon-rich domains. Furthermore, UV-Vis and FTIR analyses confirmed the non-toxic nature of the engineered biomass.