Novel Eco-Friendly Benzotriazole Amide Derivatives as Multifunctional Lubricant Additives with Enhanced Corrosion Inhibition and Tribological Performance

To alleviate the environmental pollution caused by conventional lubricant additives containing sulfur, phosphorus, and heavy metals, this study designed and synthesized two novel eco-friendly benzotriazole amide derivatives: N-oleoyl-N'-(1H-benzotriazol-1-ylmethyl)diethylenetriamine (O-BT-DETA) and N-oleoyl-N'-(1H-benzotriazol-1-ylmethyl)triethylenetetramine (O-BT-TETA). The target compounds were prepared via covalent conjugation of benzotriazole with oleic acid, using diethylenetriamine and tetraethylenepentamine as bridging linkers. In a 0.5 mol/L H₂SO₄-75% ethanol/water solution, both compounds exhibited excellent corrosion inhibition performance on Q235 carbon steel. At a concentration of 10.0 mM, the corrosion inhibition efficiency of O-BT-TETA reached up to 87.7%. Furthermore, tribological tests demonstrated that both O-BT-DETA and O-BT-TETA as additives of PEG200 could decrease the friction coefficient and wear scar diameter of the base oil at 25 °C and 100 °C and O-BT-DETA showed better anti-friction and anti-wear properties than O-BT-TETA. With the addition of 3.0% O-BT-DETA, the friction coefficient of the PEG200 base oil decreased by 54.12% at 25 °C and 44.69% at 100 °C. Thermodynamic analysis of the electrochemical data revealed that the adsorption of O-BT-DETA and O-BT-TETA on Q235 steel conformed to the Langmuir monolayer adsorption model, and physisorption was the dominant mechanism. XPS analysis of the worn surface further confirmed that O-BT-DETA and O-BT-TETA initially adsorbed physically onto the metal surface and then underwent interfacial tribochemical reactions to form protective tribofilms. This study provides a theoretical basis and technical support for the design and application of novel eco-friendly anti-corrosion lubricant additives.