Corrosion and Inhibitor on Material: Experimental and Computational Calculations

Abstract

In this paper, we provide a comprehensive study of corrosion inhibition of mild steel in 1 M HCl solution at 313, 323, and 333 K using 4,4-Dimethyl oxazolidine-2-thione (DMOT) and its protonated form (DMOTH+) as inhibitors. Our results show that the corrosion rate of mild steel in 1 M HCl increases as the temperature increases while it decreases as the DMOT concentration increases. In contrast to the corrosion rate, the DMOT inhibition efficiency decreases with temperature and increases with increasing DMOT concentration. Both experimental and quantum chemical computational results reveal that the adsorption of DMOT and DMOTH+ on the mild steel surface is a mixed-type process having both physisorption and chemisorption. Moreover, the inhibitor adsorption on the mild steel surface was found to obey the Langmuir adsorption isotherm and the value of Gibbs energy of adsorption at the three studied temperatures is associated with an adsorption mechanism involving both physisorption and chemisorption processes. Heavy corrosion, cavities, and pitting of surfaces were observed in the absence of DMOT inhibitor, while much less corrosion was consistently observed in the presence of DMOT inhibitor.