Use of expired Sulbutiamine drug as anticorrosive agent for carbon steel in hydrochloric acid solution

Sulbutiamine is a synthetic drug that has many medical applications. In this paper it was studied as a potential corrosion inhibitor in a 1 M HCl solution. Several electrochemical measurements including weight loss (WL), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and electrochemical frequency modulation (EFM) tests were employed in this study. The test demonstrated that the Sulbutiamine drug's inhibitory efficacy increased with increasing concentration and decreased with temperature. This medication binds to the surface of carbon steel according to the Temkin and Freundlich adsorption isotherms. The inhibition can be attributed to the reduction of the exposed carbon steel surface area to the HCl solution due to the creation of a barrier film. According to weight loss studies, Sulbutiamine effectively inhibits corrosion of carbon steel, with an efficacy of 95.2% at 300 ppm. According to PDP measurements and EIS analysis, Sulbutiamine functions as a mixed-type inhibitor that shows a decrease in the double layer values and an increase in the charge transfer resistance when increasing the inhibitor concentration. The thermodynamic parameters were calculated and showed that the free energy of the adsorption indicated a spontaneous adsorption process and a stability of the adsorbed film. Using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), the surface morphology of the carbon steel samples was evaluated. Quantum chemistry calculations and molecular dynamics calculations were further utilized to investigate and validate the inhibition process and mechanism.