Green Synthesis and Evaluation of a Novel Dihydropyridine Corrosion Inhibitor for Carbon Steel in Acidic Environments: Experimental and Theoretical Studies

A green and efficient one-pot synthesis route in deep eutectic solvents (DESs) led to the successful preparation of the thienyl-pyridine derivative 4-(4-chlorophenyl)-2-oxo-6-(thiophen-2-yl)-1,2-dihydropyridine-3-carbonitrile. This study aims to develop an environmentally friendly, and non-toxic method for synthesizing effective corrosion inhibitor. To explore its anticorrosive properties, the pyridine derivative was tested against carbon steel (CS) corrosion in 1.0 M hydrochloric acid using electrochemical techniques. The experiment's results indicate that the substance under investigation is a powerful CS inhibitor in 1.0 M HCl solution, achieving an inhibition efficiency of up to 93%. It serves as an inhibitor of mixed types. A reduction in the compound’s effectiveness was observed upon increasing the temperature and lowering the inhibitor concentration. The inhibition mechanism of the inhibitor was largely dependent ᴏn the inhibitor molecules' adsᴏrption on CS surface, and it obeys the Langmuir adsᴏrption isotherm. This study explores interaction mechanisms of the CPT molecule on Fe (110) surfaces and its chemical reactivity through Mᴏnte Carlo simulation (MC), and density functional theory (DFT). Quantum chemical parameters including ionization potential, electron affinity, electronegativity, and electrophilicity reveal that CPT exhibits balanced reactivity, facilitating its effective interaction with the Fe (110) surface. DFT results corroborate the MC simulations, confirming strong and competitive adsorption of CPT in aqueous environments.