Theoretical Investigations on Thiadiazole Derivatives as Corrosion Inhibitors on Mild Steel

Experimental methods have been employed to elucidate the corrosion inhibition mechanism, but they are often expensive and time-consuming, necessitating the search for more alternatives. The development of computer hardware and software engineering has allowed the effective use of theoretical modeling tools that successfully correlate the inhibition efficiency of the inhibitors with their molecular structure and properties. In this study, computational methods were used to further explain the mode and mechanism of the thiadiazoles inhibition on Fe surface whose studies were reported in the literature as Thiadiazoles-A potential class of heterocyclic inhibitors for prevention of mild steel corrosion in hydrochloric acid solution. Parameters including quantum chemical through DFT and molecular dynamic simulations of studied molecules on Fe surfaces were performed. Results obtained by calculating these thiadiazoles' adsorption or binding energies were in good agreement with the experimentally reported results elsewhere. Concerning the calculated adsorption or binding energies, their relatively low values inferred that the compounds are weakly adsorbed onto the surface of Fe through Van der Waals forces and therefore obey the mechanism of physical adsorption. Fukui indices values revealed that the active sites were found to be located on the molecules heteroatoms (Sulphur and Nitrogen). It was also established that the reference molecule thiadiazole (TDA) was the least adsorbed when compared to the other four molecules of its derivatives. The order of the inhibition efficiency as determined is as follows: PAT > EAT > MAT > AT > TDA