Synthesis, experimental, quantum chemical and molecular dynamics study of carbon steel corrosion inhibition effect of two Schiff bases in HCl solution

Two new benzohydrazide Schiff bases, (Z)-2-hydroxy-N'-(2-hydroxy-1,2-diphenylethylidene) benzohydrazide (B1) and (Z)-2-hydroxy-N'-(2-oxo-1,2-diphenylethylidene) benzohydrazide (B2) were synthesized and examined as carbon steel corrosion inhibitors in 1.0 mol L-1 HCl using weight loss (WL) method, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), Quantum chemical calculations (QCC) and molecular dynamics (MD) simulations. Results showed that both studied Schiff bases are adsorptive corrosion inhibitors, which obeys Langmuir adsorption with predominantly chemisorption. The maximum inhibition efficiencies (based on WL results) were obtained 94.0% and 96.5% for B1 and B2, respectively. Thermodynamics of the adsorption process was studied and the activation parameters of the corrosion reaction were also calculated and discussed. The calculated electronic parameters, E-HOMO, E-LUMO, the energy gap between HOMO-LUMO and dipole moment could well explain the order of inhibition efficiencies. Molecular dynamic simulations revealed that the inhibitors adsorbed in an almost planar manner, leading to a more efficient adsorption and inhibition. (C) 2019 Elsevier B.V. All rights reserved.