Electrochemical, Spectrochemical and Quantum Chemical Studies on Dimedone as Corrosion Inhibitor for Copper in Acetonitrile

A number of techniques have been applied in the investigation of inhibition abilities of dimedone
(DMD) for copper in acetonitrile at 25°C. By potentiodynamic polarization and electrochemical
impedance spectroscopy (EIS), the corrosion resistance was found to be increased with inhibitor
concentration up to 93.68% inhibition efficiency at 3.00 mM, indicating that DMD molecules can
cumulatively adsorb on the copper surface and finally form a protective film on copper-solution
interface. This is also supported by the decreasing of copper oxidation in cyclic voltammogram.
Polarization curves revealed that DMD is of mixed type inhibitor.
The adsorption of DMD on copper surface obeys the Langmuir isotherm and the adsorption
mechanism is of physisorption type. The values of standard energy of adsorption (ΔGo
ads) were found
to be in good agreement for both polarization and impedance techniques to be -8.17 and -8.43
kJmol-1 respectively. Fourier Transform Infrared spectroscopy (FT-IR) confirmed the interaction of
copper with oxygen on DMD. The mole ratio method suggested that the complexation ratio of copper-
DMD is 1:2. Scanning electron microscopy (SEM) of copper surface after immersion in DMD solution
indicates the presence of a protective layer on the electrode surface. The frontier molecular orbital
energy EHOMO (highest occupied molecular orbital), ELUMO (lowest unoccupied molecular orbital) and
the Mulliken charge distribution obtained from Quantum chemical calculations revealed (ΔE) for DMD
0.2091 hartree, reflecting strong adsorption of the molecules on copper surface. The enhanced
corrosion inhibition is possibly due to the compact film structure blocking electron transfer at the
electrode surface. This provides a typical example in understanding the system as well as
interpretation of the data by both traditional and advanced technology to support the newly coming
technology which would make science much more fruitful.