Substituted 2-imidazoline derivative: New and efficient corrosion inhibitors for mild steel in sulphuric acid solution
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Date
2014
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Abstract
The aim of this work is to obtain deeper insight into the mechanism of the protective
action of the imidazole-based corrosion inhibitor, 2-(4'-N, N-Dimethylaminophenyl)-imidazoline
(DMAP2l). Investigations were performed on mild steel in 0.5 M H2 SO4 by electrochemical
methods and non - electrochemical methods. Maximum protection efficiency reaches about
85% for DMAP2I at 200 ppm concentration level. The adsorption of the imidazoline derivative
on mild steel surface follows Langmuir and Tempkin isotherm. The adsorption free energy on
mild steel (20 — 30 kJ/mol) reveals a comprehensive (physical and chemical) adsorption of the
inhibitors on the metal surface. Polarization curves reveal that DMAP2l act as a mixed-type
inhibitor. Results obtained from potentiodynamic polarization and impedance measurements are
in good agreement. Quantum chemical method is used to explore the relationship between the
inhibitor molecular properties and its inhibition efficiency. The density function theory (DFT) is
also used to study the structural properties of the inhibitor. It is found that when the imidazole
derivative adsorbs on the mild steel surface, molecular structure influences their interaction
mechanism. The inhibition efficiencies of the compound showed a certain relationship to highest
occupied molecular orbital (HOMO) energy and Mulliken atomic charges.