Inhibition of copper corrosion in acid medium by imidazole-based compounds:electrochemical and molecular approaches

Abstract

Chemically modified imidazole molecules: 4-(1H-imidazol-1-yl)aniline, 4-(1H-imidazol-1-yl)benzaldehyde, 4-(1H-imidazol-1-yl)phenol and (4-(1H-imidazol-1-yl)phenyl)methanol were investigated as inhibitors of the copper (Cu0) corrosion in 0.5 mol L-1 H2SO4 medium.The electrochemical corrosion data were obtained by monitoring open circuit potential, linear potentiodynamic polarization and electrochemical impedance spectroscopy techniques, while the computational density functional theory (DFT) method was applied to correlate the electronic properties of the molecules with corrosion inhibition efficiencies. All molecules had inhibited the Cu corrosion, and the inhibition values lied between 80 and 94%. A good correlation between the inhibition efficiencies values and Gibbs adsorption energy was found, showing that the more negative Gibbs energy, better interaction between the corrosion inhibitor with the Cu0 surface, diminishing its corrosion in 0.5 mol L-1 H2SO4 medium. The DFT calculations showed significative differences in electronic and reactivity properties of imidazole and other molecules. The higher corrosion inhibition of imidazole derivates could be explained by electrophilic characteristic of these molecules, since there are empty molecular orbitals spread over mainly in benzene rings that make a metal-ligand charge transfer, receiving electronic density from the copper surface by backbonding, according to the electronic Fukui functions and the potential charge distribution considering the map of electrostatic potential.