Experimental and theoretical evaluation of a newly synthesized quinoline derivative as corrosion inhibitor for iron in 1.0 M hydrochloric acid solution

Abstract

A novel 2-[(6-ethyl-4-hydroxy-2,5-dioxo-5,6-dihydro-2H-pyrano [3,2-c]quinolin-3-yl)methylidene]hydrazinecarbodithioic acid (EHDM) was successfully synthesized, and its chemical structure was proved based on its correct elemental analysis and spectral data (IR, 1H NMR, 13C NMR and mass spectra). The corrosion inhibition performance of EHDM for iron in 1.0 M HCl solution was investigated using electrochemical techniques at inhibitor concentrations (10−7–10−3 M), surface analysis, density functional theory (DFT) and molecular dynamic simulation (MD). The corrosion inhibition efficiency was effectively enhanced with increasing the concentrations of EHDM, The provided Tafel polarization results revealed that the EHDM promote the suppression both the cathodic and anodic reactions behaving as mixed-type inhibitor mainly anodic process. Langmuir's adsorption isotherm was confined as best fitted isotherm describes the physical-chemical adsorption capability of the EHDM on the iron surface with change in the free energy of adsorption ΔGads=-39.5 kJmol−1.The surface morphology techniques SEM/EDX and AFM revealed that, the EHDM inhibitor is confined on the surface of the iron. The computational study based on DFT/B3LYP method simulations with 6–311++G (d,p) basis sets and Molecular Dynamics (MD) simulations revealed the correlation between the EHDM molecular chemical structure and its anti-corrosive property.