الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
Electrochemical frequency modulation (EFM) can be used as a rapid and non-destructive technique for corrosion rate measurements without prior knowledge of Tafel constants. Corrosion rates obtained with this technique were in good agreement with other traditional techniques as Tafel extrapolation and EIS. Causality factors used by EFM are good internal check for verifying the validity of data obtained by this technique.
The corrosion inhibition of iron in 1 M hydrochloric acid solution by some new thiourea derivatives, 9-(4-fluorophenxyl aminothioxo)carbazole (FPAC), 1-octayl-3-phenyl- thiourea
(OPT), 1, 3-diarylidenethiourea (DAT), 1-(2-hydroxyphenyl)-3-phenylthiourea (HPP), and 1-(anthraquinon) thiosemicarbazone
(ATC) was studied using the following techniques: Tafel extrapolation method, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM). These measurements show that the inhibition efficiency increased by increasing the inhibitor concentration. The inhibition efficiency follows the order: FPAC > OPT > HPP > DAT > ATC.
Polarization studies show that these compounds act as mixed type inhibitors in 1 M HCl solution. The effect of temperature on corrosion inhibition was studied using polarization technique. The fundamental thermodynamic parameters for dissolution and adsorption were determined and discussed. These inhibitors function through adsorption following Flory-Huggins and kinetic-thermodynamic model isotherm. Equivalent circuits of the investigated system are suggested.
The electronic properties of these inhibitors, obtained using MNDO semi-empirical self-consistence field method, have been correlated with their experimental efficiencies using non-linear regression method.
Keywords: iron; corrosion; EFM; EIS; Tafel; MNDO; acid inhibition