Theoretical and electrochemical evaluation of 2-thioureidobenzheteroazoles as potent corrosion inhibitors for mild steel in 2 M HCl solution

• Published in: Journal of molecular liquids 2020-12, Vol.319, p.114081, Article 114081
• Main Authors: Murthy, Ram, Gupta, Parth, Sundaresan, C.N.
• Format: Article
• Language: English
• Subjects: Impedance (EIS); Mild steel, acid corrosion; Polarization (PDP); SEM; Thermodynamic parameters
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2020.114081

Corrosion Inhibition potential of three 2-thioureidobenzheteroazoles, namely, 2-thioureidobenzoxazole (BOT),2-thioureidobenzimidazole (BIT), 2-thioureidobenzothiazole (BTT) compounds were predicted theoretically using quantum chemical calculations on type CS 1084 carbon steel in 2 M HCl at 25 °C. DFT calculations indicated that BTT showed better inhibition compared to BIT and BOT compounds. Theoretical conclusions were subsequently validated by experiments carried out using Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP) and Scanning Electron Microscopy (SEM). Adsorption of 2-thioureidobenzheteroazoles on the steel surface obeyed the Langmuir adsorption model. Thermodynamic parameters indicated that, the adsorption process is energetically spontaneous, while the calculated kinetic parameters corroborated the adsorption phenomenon at the metal/solution interface. Furthermore, PDP results showed that, the inhibitors behaved as mixed type inhibitors with cathodic dominance. The maximum corrosion inhibition efficiency obtained was 96.1% for BTT at 2 mM concentration. The surface morphology investigations using SEM technique showed lower corrosion inhibition in presence of these inhibitors. Sulphur and nitrogen heteroatoms served as reactive centres for the adsorption of inhibitors, based on the quantum chemical calculations. [Display omitted] •The quantum calculations were validated by experimental measurements on inhibition properties of 2-thioureidobenzheteroazoles.•The synergistic effects of thiourea and benzheteroazole moieties on mild steel surface in 2M HCl were investigated.•2-thioureidobenzothiazole has been found to be the most potent corrosion inhibitor for mild steel (MS).