Synthesis, DFT, molecular dynamics, and Monte Carlo simulation of a novel thiourea derivative with extraordinary inhibitive properties for mild steel in 0.5 M sulphuric acid

Abstract

A novel thiourea derivative has been successfully synthesized via green routes and fully characterized by FT-IR, ¹H, ¹³C-NMR, and elemental analysis. The synthetic inhibitor 2-amino-N-(phenylcarbamothioyl) benzamide (APCB) was assessed as a corrosion inhibitor for mild steel (MS) in 0.5 M H₂SO₄. Various electrochemical techniques, such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), have been used to evaluate inhibition efficiency. As a result, EIS and PDP agreed with each other, indicating that APCB exhibits an inhibition performance that exceeds 96% at a concentration of 2 × 10⁻⁴ M and increases with an increase in temperature up to 98% at 333 K. However, PDP measurements showed that APCB is a mixed type of inhibitor. In addition, SEM, EDX, AFM, and contact angle measurements were used as a topological surface characterization technique that confirmed the formation of a protective layer over the MS surface. Additionally, the complex formation was thoroughly confirmed by UV-Vis measurements. The adsorption of APCB proved the highest compliance with the Langmuir adsorption isotherm. Furthermore, density functional theory (DFT) calculations were conducted to establish the correlation between the electronic structure and excellent inhibition efficiency. Moreover, molecular dynamics (MD) simulations were used to find interaction energy in different media. Finally, the adsorption affinity of the MS surface for different concentrations of APCB was verified via Monte Carlo (MC) simulations. Owing to the outcomes of this study, it is remarkable that APCB, with its low cost and simple synthesis, might be an exceptionally prominent option for mild steel protection.