Novel eco-friendly nicotinonitrile derivative as a corrosion inhibitor for carbon steel: Synthesis, inhibitive efficiency, and DFT analysis

Two new variations of Nicotinonitrile were synthesized, namely: "4-(4-Chlorophenyl)-3-cyano-6-(thien-2-yl)-1Hpyridin-2-one (3A) and 4-(4-Chlorophenyl)-2-oxo-1-(prop-2-yn-1-yl)-6-(thien-2-yl)-1,2-dihydropyridine-3-carbonitrile (4A). The chemical structures were examined and confirmed using IR and 1H NMR. This method's notable features include being solvent-free, catalyst-free, economical, and having great yields without the need for a catalyst. These compounds were then evaluated as corrosion inhibitors for carbon steel (CS) in 1 M HCl media. Both weight loss (WL) and electrochemical methods such as potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were employed for the investigation. The synthesis and assessment of a novel series of organic compounds with related chemical structures as hydrochloric acid corrosion inhibitors of C-steel is a novel aspect of this study. The results showed that the Nicotinonitrile derivatives were effective corrosion inhibitors, with inhibition efficiencies (%eta) of 86.4% and 90.7% for 3A and 4A, respectively, at a concentration of 15x10- 5 M. Theoretical computations are applied using the density functional theory. The experiments' findings show that these compounds are effective corrosion inhibitors, and that the concentration of the substances increases the inhibition efficiency. When compared to 3A, the 4A molecule has the maximum efficiency. Monte Carlo simulations and quantum chemical calculations were also performed to analyse and discuss the behaviour of these derivatives. Surface analysis using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) was conducted to verify the results obtained from atomic force microscope measurements. Excellent agreement is found between the outcomes of theoretical computations and experimental measurements.