Novel N-heterocyclic Schiff base based on Isatin derivative as a sustainable, eco-friendly, and highly efficiency corrosion inhibitor for carbon steel in sulfuric acid medium: Electrochemical and Computational investigation

The present study aimed to synthesize and investigate the inhibitory effects of two novel Schiff bases namely: (Z)- 1-(5-nitro-2-oxoindolin-3-ylidene) semicarbazide (NOSC) and Z)- 1-(5-nitro-2-oxoindolin-3-ylidene) thiosemicarbazide (NOTSC) for carbon steel (CS) corrosion in 0.5 M H2SO4 medium. Through chemical and electrochemical investigations, the efficiency of NOSC and NOTSC's corrosion inhibition was ascertained experimentally at 298 K. It is noteworthy that the inhibitory efficacy of NOTSC and NOSC reached 93.4% and 91.6%, respectively, at a concentration of 10-3 M. Studies using potentiodynamic polarization revealed that NOTSC and NOSC functioned as mixed-type inhibitors. A depressed capacitive loop with varying concentrations is the primary way that the Nyquist plot of impedance is represented. The transportation of corrosive ions to the metal substrate is impeded by the adsorption of both NOSC and NOTSC, as determined by the Langmuir isotherm. Apart from the chemical and electrochemical investigations, additional insights were gained into the inhibitory mechanism by the application of density functional theory (DFT), molecular dynamics simulation (MDS), and an understanding of the molecular structure of NOTSC and NOSC. A robust correlation was discovered between the theoretical and experimental results through the application of DFT/MDS computational study.