Anti-corrosion investigation of a new nitro veratraldehyde substituted imidazopyridine derivative Schiff base on mild steel surface in hydrochloric acid medium: Experimental, computational, surface morphological analysis

V Shenoy and PP Venugopal and PDR Kumari and D Chakraborty, MATERIALS CHEMISTRY AND PHYSICS, 281, 125855 (2022).

DOI: 10.1016/j.matchemphys.2022.125855

Intensive research has recently been directed toward synthesizing novel, non-toxic, and cost-effective organic inhibitors against metallic corrosion. In the present investigation, a non-toxic, novel Schiff base inhibitor, 6bromo-(4,5-dimethoxy-2-nitrophenyl) methylidene imidazo1,2-a pyridine-2-carbohydrazide (NVAIP) was synthesized and tested for its corrosion inhibition performance on Mild Steel (MS) in 1 M HCl at 303-323 K using potentiodynamic polarization study, electrochemical impedance spectroscopy (EIS) measurements, Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM) and XRay Photoelectron Spectroscopy (XPS) analyses. The electrochemical results stated the inhibition effectiveness (n %) of NVAIP was dependent on concentration and temperature, with the maximum efficiency (92.3%) recorded at 303 K for 500 ppm. The mixed-type inhibitory effect of NVAIP was substantiated by the polarization test results. The Langmuir adsorption isotherm model accorded with the metal surface evaluated, and Gibbs free energy of adsorption values ranged from - 35.05 to-36.05 kJ/mol, implying a physical and chemical adsorption mechanism. Surface morphological analysis was carried out to characterize the chemical composition of the adsorbed inhibitor on the MS surface, and these techniques confirmed that the inhibitive layer is composed of an iron oxide/hydroxide mixture where NVAIP molecules are incorporated. Further, the physicochemical and electronic properties of the NVAIP were investigated using Density Functional Theory (DFT) and electrostatic potential energy mapping (ESP). Delta Eads value of -57.21 kcal/mol obtained from Molecular Dynamic (MD) simulations correlates well with the experimental results. Moreover, the relevance of the molecular structure of NVAIP and its inhibition act was validated by quantum chemical calculations and molecular dynamic (MD) simulation studies. A possible inhibition mechanism was proposed based on the experimental, theoretical, and surface analysis results. The outcomes of all the techniques show consistent agreement with each other.

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