Abstract
The corrosion inhibition properties of 2,6-diphenylpiperidin-4-one (DPP) (1A) and 2,6-diphenyldihydro-2H-thiopyran-4(3H)-one (DPDT) (1B) for mild steel in 1 M phosphoric acid were studied using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The effect of temperature on the corrosion behavior of mild steel has been examined in the temperature range 303 - 328 K. The inhibition efficiency increases with increasing inhibitor concentration but decreases with increasing temperature. Potentiodynamic polarization studies indicated the mixed nature of inhibitors. The adsorption of the inhibitors on mild steel surface obeyed the Langmuir adsorption isotherms. The density functional theory (DFT) at the B3LYP/6- 31G (d) basis set level was performed on 1A and 1B to investigate the correlation between molecular structure and the corresponding inhibition efficiency (%). The quantum chemical parameters such as EHOMO, ELUMO, the energy gap (E), hardness (η), softness (S), dipole moment (μ), electron affinity (A), ionization potential (I), the absolute electronegativity (χ), the fraction of electron transferred (N), electrophilicity index (ω), the back-donation (EBack-donation) and Mulliken population analysis have been calculated.
Highlights
The protection of metal surface against corrosion is an important industrial and scientific topic
The surface of the specimens was cleaned by distilled water, dried and weighed in order to calculate the corrosion rate (CR) and inhibition efficiencies (%)
The results show that the corrosion rate decreases with increasing concentration of the inhibitor and the inhibition efficiency increases
Summary
The protection of metal surface against corrosion is an important industrial and scientific topic. (2014) Quantum Chemical Studies on the Corrosion Inhibition of Mild Steel by Piperidin-4-One Derivatives in 1 M H3PO4. Among these approaches the use of corrosion inhibitors is the most common. There has been increasing use of the density functional theory (DFT) methods as a theoretical tool in elucidating the mechanism of corrosion inhibition of heterocyclic organic compounds by several researchers [2]-[5]. Quantum chemical methods have already proven to be very useful in determination of the molecular structure as well as elucidating the electronic structure and reactivity
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