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.
