A combined experimental and theoretical study into the effect of new heterocyclic compound containing β-lactam ring as corrosion inhibitor for mild steel in hydrochloric acid

In this study, a new corrosion inhibitor termed 2-(3-chloro-2-(4-hydroxy-3, 5-dimethoxyphenyl)-4-oxoazetidin-1-yl)-1-methyl-1H-imidazole-4(5H)-one (COMI) has been synthesized, diagnosed, and tested as a potential candidate for mild steel corrosion prevention in 1M HCl. The research combined experimental and theoretical approaches. Experimentally, weight loss, electrochemical tests, FTIR, 1 H NMR, 13 C NMR, EDS, surface morphology analysis, hardness assessments, thermal stability studies, and contact angle measurements were conducted. Computationally, density functional theory (DFT) and an inhibitory mechanism were proposed to explain the inhibitor–metal surface interactions. The study demonstrated that COMI significantly reduced corrosion rates in 1M HCl, achieving an inhibition efficiency of 98.42% at a concentration of 80 ppm and a temperature of 60 °C. The inhibitor was found to form a protective layer on the mild steel surface, influencing both anodic and cathodic corrosion processes. This protective layer formed spontaneously, consistent with the Langmuir adsorption isotherm. The Gibbs free energy (ΔG ads ) was calculated to be −28.81 kJ/mol, indicating that COMI adsorbed spontaneously onto the mild steel surface through both physical and chemical adsorption mechanisms. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images confirmed the existence of this protective layer. The addition of 80 ppm COMI reduces the surface roughness from 2.12 to 0.28 μm. Computational studies further validated the experimental findings, confirming the formation of bonds between COMI and the mild steel surface.