Adsorption Behavior of Thiadiazole as Corrosion Inhibitors on Copper Surface

Abstract

Adsorption behavior of four typical thiadiazole derivatives as corrosion inhibitors on copper surface both in vacuum and aqueous media, including 1,3,4-thiadiazole-2,5-mercapto (T-SH), (1,3,4-thiadiazole-2,5-diyl) bis (sulfanol) (T-OH), S,S'-(1,3,4-thiadiazole-2,5-diyl) bis (O-hydrogen carbonothioate) (T-COOH) and O,O'-dimethyl S,S'-(1,3,4-thiadiazole-2,5-diyl) bis (carbonothioate) (T-COOCH3), has been theoretically studied using quantum chemistry calculations and molecular dynamics simulations method, and the corrosion inhibition mechanism has been analyzed. The present conclusions have been experimentally verified by corrosion test. Global activity indices indicate that T-OH has the highest reaction activity among the four molecules both in vacuum and aqueous environment. The reaction activity of T-SH is little weaker than T-OH. For the two other molecules, Fukui indices suggest that T-COOCH3 possesses five electrophilic attack centers, which enable multi-center adsorption of the molecule on metal surfaces and thus it has a preferable corrosion inhibition performance compared to T-COOH in vacuum. However, T-COOH has the higher reaction activity in aqueous. At the same time, molecular dynamics results show that T-COOCH3 is more stably adsorbed on copper with surface (110) crystallographic plane than T-COOH does both in vacuum and aqueous environment when the interaction of the inhibitor molecules with four layers of copper atoms is considered. The theoretical results show that the efficiency of the four inhibitors accorded well with experimental results. The study of the questions of oxidation and discoloration of copper surface is to be provided a new method.