Influence mechanism of phenolic-amine antioxidant composite on biodiesel-induced metal corrosion: The role of competitive adsorption

The addition of antioxidant composites significantly improves the antioxidant properties of biodiesel while reducing its corrosive properties, but the corrosion inhibition properties are often variable. This study aims to investigate the role of phenolic and amine antioxidant composites in mitigating biodiesel-induced metal corrosion, focusing on the performance and mechanism of antioxidant composites on corrosion inhibition. The results indicate that antioxidants composites cause competitive adsorption among the antioxidant molecules on the Cu surface. Notably, amine-amine antioxidant composites exhibit stronger competitive adsorption than phenolic-phenolic composites. The compatibility of adsorption energies of antioxidants on the metal surface significantly affects this competitive adsorption. The smaller the disparity in adsorption energies between two antioxidants, the more pronounced the competitive adsorption, resulting in a reduced corrosion inhibition effect. Regarding the corrosion inhibition mechanism, the composited antioxidants are initially adsorbed onto the Cu surface. Once the antioxidants are depleted, Cu interacts with biodiesel, circumventing the initial reaction between Cu and biodiesel constituents, thereby reducing biodiesel's corrosiveness. These findings provide insights for optimizing antioxidant combinations to enhance biodiesel stability and reduce corrosive damage to storage and engine components.