Integrated Computation and Experimental Investigation on the Adsorption Mechanisms of Anti-Wear and Anti-Corrosion Additives on Copper

We integrated first-principles calculations and surface characterization techniques to reveal a new molecular adsorption mechanism of antiwear (dialkyl dithiophosphate ester, EAK) and anticorrosion (2,5-bis(ethyldisulfanyl)-1,3,4-thiadiazole, DTA) additives on the Cu surface during the rolling process. For direct comparison of modeling and experiments, the Cu(110) surface was used in the model based on the strong (220) preferred orientation observed in the microstructures of the rolled copper foil. Density functional theory (DFT) calculations were performed to obtain the adsorption energy, the optimized adsorption structures, and the charge transfer due to adsorption for EAK and DTA on the Cu(110) surface. It was found that the anticorrosion additive, DTA, decomposed and chemically adsorbed on the Cu(110) surface strongly via multiple Cu-N and Cu-S bonds, while the antiwear additive, EAK, adsorbed weakly due to one Cu-O bond. The predicted chemical bonds formation with the Cu surface reasonably agreed with X-ray photoelectron spectroscopy (XPS) analysis. A new anticorrosion mechanism, due to DTA decomposition and stronger chemisorption than that of EAK, was therefore proposed based on the simulation.