A multianalytical approach to benzodiazepine derivatives for the corrosion protection of mild steel in HCl solutions: Electrochemical analysis, SEM/EDX, XPS, DFT, and MDS calculations

This study takes a detailed look at the corrosion inhibition capabilities of two benzodiazepine-derived organic compounds, 3,3-dimethyl-11-(4-nitrophenyl)-2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]diazepin-1-one (PNO) and 3,3-dimethyl-11-(2-nitrophenyl)-2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]diazepin-1-one (ONO), in a 1.0-M hydrochloric acid environment using a variety of analytical methods, including electrochemical approaches - electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization (PDP). The results show that the concentration-dependent inhibitory efficacy of PNO and ONO increases with increasing concentration. Both inhibitors exhibit mixed-type behaviour, which is confirmed by the polarization results. At the optimum concentration, the inhibition efficiencies of PNO and ONO are 92.9% (PNO) and 87.6% (ONO), respectively. The effective adsorption of these inhibitors on the metal surface was also confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The existence of a barrier layer surrounding the mild steel was demonstrated using scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX), all of which were used to study the surface characterization. The most important interactions with the iron surface are achieved by inhibitors with electron-accepting properties, according to density functional theory results and molecular dynamic simulation (MDS). With encouraging prospects for industry and metal preservation, these results pave the way for promising applications for effective corrosion protection in a 1.0-M HCl environment.