The roles of mercapto, benzene, and methyl groups in the corrosion inhibition of imidazoles on copper: II. Inhibitor–copper bonding

Abstract

Bonding of five imidazole type molecules—imidazole, 1-methyl-imidazole, benzimidazole, 2-mercapto-1-methyl-imidazole, and 2-mercaptobenzimidazole—with copper surfaces and hydrated Cu2+ ions is characterized in detail by DFT calculations as to explain the corrosion inhibition efficiency trend of these inhibitors for copper, determined experimentally in the Part I. We find that mercapto-substituted imidazoles are prone to deprotonation upon adsorption. They bond stronger to the surface and display weaker tendency to form soluble complexes with hydrated Cu2+ ions than non-mercapto molecules. By encapsulating these two interactions into a simple model—the first interaction is deemed as beneficial and the second as detrimental—the inhibition efficiency trend is well captured.