Novel triphenyl imidazole based on 8-hydroxyquinoline as corrosion inhibitor for mild steel in molar hydrochloric acid: experimental and theoretical investigations
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The preventing effect of novel triphenyl imidazole based on 8-hydroxyquinoline (HDiPIQ) on the corrosion attack of mild steel in 1 M HCl solution was investigated. Electrochemical impedance and potentiodynamic polarization measurements have been realized. Inhibitor concentration increase leads to a considerable shift in mild steel oxidization rate in molar hydrochloric acid solution with inhibitive efficiency such as 89% at 10–3 M concentration of HDiPIQ. Tafel curves showed that HDiPIQ acted as a mixed-type inhibitor. Nyquist curve drawing showed that inhibitor concentration getting increased resulted in polarization resistance growth, that involves inhibition efficiency increase and double-layer capacitance decrease. The effect of temperature in the range 298–328 K at a concentration of 10–3 M HDiPIQ showed that inhibiting efficiency diminished slightly with temperature. HDiPIQ adsorption on steel surface has been found to comply with Langmuir’s isotherm model, implying a mixed type of binding with predominance of chemical adsorption mechanism. Activation energy and thermodynamic results such as enthalpy, entropy and free energy have been determined and discussed. Surface characterization using scanning electron microscopy allowed the confirmation of HDiPIQ inhibiting effect on mild steel corrosion. UV–visible spectroscopy results have been analyzed and discussed. Quantum chemical factors such as the frontier molecular orbitals energies (EHOMO and ELUMO), the energy gap between ELUMO and EHOMO (ΔE), hardness (η), electronegativity (χ), and Fukui indexes have been calculated and discussed using density functional theory calculations and the Becke’s three-parameter exchange functional with the Lee–Yang–Parr correlation function and the 6–311 + G(d,p) basis set. Monte Carlo simulation allowed elucidating inhibitor/mild steel interaction of the above-mentioned inhibitor molecule.

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