2-Amino-4-(4-methoxyphenyl)-thiazole as a novel corrosion inhibitor for mild steel in acidic medium

The inhibitory effects of 2-amino-4-(4-methoxyphenyl)-thiazole (MPT) on mild steel corrosion were evaluated in 0.5 M H₂SO₄ and 1 M HCl solutions, respectively. From the analysis of potentiodynamic polarization curves and electrochemical impedance spectroscopy, MPT can effectively inhibit the corrosion of mild steel in acidic solutions. Under the optimal conditions, the inhibition efficiency (η) was as high as 95% in 0.5 M H₂SO₄ solution. The inhibition property of MPT was much better than that of the reported corrosion inhibitor 2-amino-4-phenylthiazole (APT). Polarization curves also demonstrated that MPT mainly inhibited the anodic corrosion of mild steel in HCl solution and the cathodic corrosion in H₂SO₄ solution, respectively. The adsorption of MPT on the surface of mild steel was found to obey Langmuir adsorption isotherm in both acid solutions. Quantum calculations suggest that the addition of electron donor group (−OCH₃) endowed the molecule better adsorption ability on mild steel surface. The interaction between protonated MPT and anions on Fe (0 0 1) surface was firstly investigated using molecular dynamic stimulations, and the results showed that with the adsorption of sulfate ions, MPTH⁺ had a superior binding energy on the surface of Fe. The investigation of UV–vis spectrum demonstrated the direct correlation of the experimental data and the theoretical calculations.