الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 164 |  |  |
| | | from | 164 | | |
Abstract
These organic compounds obey Langmuir adsorption isotherm showing that the inhibition is by adsorption. The degree of surface coverage (θ) of the inhibitors was found to increase with increasing the concentration of the inhibitors in the corrosive medium. The effect of temperature on the corrosion inhibition of zinc in 0.2M HCl was determined over the temperature range 30-500C using weight loss measurements. The rate of corrosion decreases with increasing the temperature indicating that the inhibition occurs through chemical adsorption of the organic compounds. Thermodynamic parameters of activation were calculated in presence of different concentrations of tested derivatives. On increasing the concentration of the inhibitor in the medium, the corrosion current is decreased.The rate of corrosion is decreased by increasing the concentration of the additives. This indicates that the presence of the inhibitors in the medium retards the corrosion of zinc in 0.2M HCL. Langmuir adsorption isotherm gives straight lines with slopes very closed to one, The Nyquist plots are not perfect semicircles as expected from the theory of EIS and this difference can be explained as follows: This behavior can be attributed to the frequency dispersion as a result of roughness and in homogeneity of the electrode surface. Increase in the diameters of this capacitive loop increase with increase of the inhibitors concenteration. charge transfer resistance Rct, and the double layer capacitance Cdl are derived from the Nyquist plots are determined for zinc in 0.2M HCl solution. The values of Rct increase with increasing the concentration of the inhibitors and this in turn leads to a decrease in corrosion rate of zinc. The decrease in Cdl can result of increase in the thickness of the electrical double layer, Intermodulation spectrum for zinc in 0.2 M HCl solution in the absence and presence of different concentrations of tested compounds were studied. The corrosion parameters such as inhibition efficiency (% IE), corrosion current density (icorr), Tafel constants (βa and βc) and causality factors; CF-2, CF-3, at different concentrations of thiazole derivatives in 0.2M HCl solution 30 ºC are calculated. The order of increased inhibition efficiency for tested derivatives is: NPT > XPT> MPT > BPT as indicated from the different methods.