Munj Biomass‐Derived Lubricant Additive Reinforced With Al–Ni, Al–Zn Borate and Ni–Al Phosphate Layered Double Hydroxides for Enhanced Tribological and Corrosion Performance of API 5L X70 Steel

In this work, a novel multifunctional bio‐derived lubricant additive was developed by combining Munj ( Saccharum munja ) biomass extract with three types of layered double hydroxides (LDHs) that is Al–Ni LDH, Al–Zn borate LDH and Ni–Al phosphate LDH synthesised via a co‐precipitation route and subsequently extracted in an ethanol–toluene mixed solvent system using a solvent‐assisted hydrothermal method. The resulting composite additive was blended with commercial SAE 20W40 engine oil (EO) at three concentrations (3, 6 and 9 mL per 100 mL of EO), designated as EO3, EO6 and EO9, respectively. Tribological performance was evaluated using ball‐on‐disc reciprocating friction tests under 20 and 30 N loads, whereas anticorrosion behaviour was assessed by electrochemical noise (ECN) measurements over 30 days. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the successful addition of LDH phases (Al–O, Zn–O, Ni–O and CO 3 2− ) with the oxygen‐rich biomass functional groups. Among all the formulations, the EO3 formulation showed the lowest surface roughness ( R a = 4.78 nm) and the near‐ideal Gaussian surface topography ( R ku = 2.91, R sk = 0.307), the lowest oxygen content in energy dispersive spectroscopy (EDS) (2.1 wt% before wear, 4.4 wt% after wear) and the most stable coefficient of friction. ECN measurements revealed progressive suppression of corrosion activity over 30 days for all additive‐modified formulations compared to the EO.