Detailed experimental and computation/molecular simulation of 1,5-benzodiazepin derivative as corrosion inhibitor for E24 steel in 1 M HCl environment

A novel synthetic chemical, namely (Z)-7-methyl-4-(2-oxopropylidene)-[1,5]-benzodiazepin-2-one (BZ-Me), was characterized using 1H NMR and 13C NMR techniques. Its ability to minimize the corrosion of E24 steel in a 1 M hydrochloric acid solution was experimentally evaluated using various techniques, including stationary electrochemical techniques (PDP), electrochemical impedance spectroscopy (EIS), density functional theory (DFT) methods, and Monte Carlo (MC) simulations. Combining EDX assessment with scanning electron microscopy (SEM) allowed for an investigation of the surface morphology of E24 steel both alone and in the presence of the inhibitor. Both approaches are in excellent agreement, indicating that the BZ-Me compound functions as a mixed inhibitor with a maximum effectiveness of 90% (according to the polarization curve) and 88% (according to the EIS methodology) for a concentration of 1 mM. In addition, the charge transfer resistance rises as inhibitor concentrations and immersion durations increase, as seen in the electrochemical impedance spectrum. Conversely, the interfacial capacitance decreases with higher inhibitor concentrations and longer immersion durations. Based on Langmuir’s isotherm, the tests have demonstrated that BZ-Me attaches to the E24 steel surface with a standard free energy |ΔG0ads| of 36.17 kJ·mol–1. This indicates that BZ-Me uses both physical and chemical adsorption to prevent the corrosion process. The surface morphological observation revealed that BZ-Me forms a barrier of protection that inhibits the transfer of active corrosive species to E24 steel surfaces, compared to the blank test. Furthermore, the offered theoretical results confirmed the experimental results obtained.