The Role of Synthesis of Heterocyclic Benzodiazepine Derivatives in the Inhibition of Carbon Steel Corrosion: Thermodynamic, Electrochemical and DFT Studies

The effect of 1,5-dihydro-1,5-benzodiazepine-2,4-dione on the corrosion of carbon steel in aerated 1.0 M HCl was investigated using gravimetric analysis, potentiodynamic polarization measurements (Tafel method), and electrochemical impedance spectroscopy (EIS). The quantum chemical properties of the inhibitor were also investigated using density functional theory (DFT). The potentiodynamic polarization results revealed that the compound acts as a mixed-type corrosion inhibitor, retarding the corrosion process by blocking active sites on the metal surface. Changes in the electrochemical impedance parameters indicated that the inhibitor (C₉H₈N₂O₂) adsorbs onto the metal surface, forming a protective layer. Thermodynamic data suggested that the adsorption process occurs predominantly through chemisorption. Furthermore, quantum chemical calculations were performed to investigate the relationship between the electronic properties of the inhibitor (C₉H₈N₂O₂) and its corrosion inhibition performance. Key parameters, including the energies of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), as well as molecular softness, were calculated and evaluated in relation to the compound's ability to inhibit corrosion.