الفهرس 
Chapter OneOnly 14 pages are availabe for public view
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Abstract
Copper is considered as one of the most popular metals which occupy a vital position in our daily life owing to its wide application in automotive industry due to its high conductivity. In present work the corrosion behavior of copper in HCl solution in absence and presence of different inorganic and organic inhibitors was studied. Different techniques, viz, open circuit potential, weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques were used. The thesis contains three chapters, (І, ІІ, Ш), Introduction, experimental and results and discusses. Chapter Ш A Discusses the chemical behaviour of Cu in hydrochloric acid solution under open circuit potential measurements * The behaviour of Cu electrode in different concentrations of HCl solution is followed by measuring the open circuit potential E as function of time. Est, found to vary with the acid concentrations according to:- Est = a1 – b1 log C HCl where a1 and b1 are constants. The value of the constant b1 decreases slightly with increasing the concentration. *It is found that the steady state potential, Est, is shifted to more positive values with increasing the concentration of the added inorganic and organic inhibitors. The inhibition effect is found to decrease according the orders:- MnO4-> MoO42- > HPO42- > CrO42- 1,4-phenylenediamine > 1,2-phenylenediamine >o-anisidine > 4-nitro- ortho-phenylenediamine. * Raising in temperature to decreases the rate of oxide film growth (to increase the rate of oxide the breakdown). *Thermodynamic functions of activation were calculated of in absence and presence of different organic compounds. Chapter Ш B The weight loss technique is used to evaluate the inhibitor efficiency of the used organic compounds as inhibitors in 0.5 M HCl, at 30 oC. *The tested inhibitor is decrease the rate of oxide film destruction. *The inhibitor efficiency increases with the inhibitor concentration and depend on its type. *The order of inhibition efficiency of investigated compounds 0.5 M HCl is found to be constituent with that obtain of from open circuit potential measurements. *The inhibition mechanism of these organic compounds seems to adsorption. *The degree of surface coverage (θ) for the inhibitors on the metal surface increases with increasing the inhibitor concentration. Chapter Ш C Potentiodynamic polarization measurements in absence and presence of inhibitors was invested of copper in 2.5x10-1M HCl. The following conclusion are:- *The corrosion current density (icorr.) decreases with increasing the concentration of the organic compounds. *The corrosion rate decreased with increasing of concentration of the organic compounds. * The presence of the organic inhibitor retards the dissolution of copper in 2.5x10-1M HCl and the degree of %IE depends on the concentration and the inhibitor type. *The order of increased inhibition efficiency for copper corrosion in 2.5x10-1M HCl at all concentrations 1,4-phenylenediamine > 1,2-phenylenediamine > 4-nitro- ortho-phenylenediamine Chapter Ш D *The results obtained from (EIS) show that the corrosion reactions in the absence and presence of organic compounds proceed under charge transfer control. *The increase in concentration of the inhibitors leads to an increase in the value of the charge transfer resistance (Rct) i.e. a decrease of the corrosion rate of copper. *The double layer capacitance (Cdl) of the corroding copper interface decreases with increase in the inhibitor concentration, suggesting an increase of the surface coverage of the inhibitor due to the adsorption of the inhibitor species at the copper surface Chapter Ш E *The electrochemical frequency modulation (EFM) technique was used as a rapid and non-destructive technique for corrosion rate measurements. *The corrosion current densities (icorr) obtained with this technique were in good agreement with those obtained from Tafel extrapolation technique. * In addition, the causality factors were good internal check for verifying the validity of data obtained by this technique. Chapter Ш F (Surface Examination by Scanning Electron Microscopy (SEM). Scanning electron microscopy were used to investigate the surface of the original mechanically polished copper specimens before and after immersion for a period 48 hours in the test solution containing 0.25M HCl and 0.25M HCl + 5x10-3M from 1,4-phenylenediamine and 1,2-phenylenediamine compounds. • from the micrographs of copper immersion in 0.25 M HCl, it is appear that surface is highly damaged due to extensive attack in the presence the uninhibited acid. Also, micrographs show less damage of the Cu-surface in presence of the organic compound. So, the attack decreases in the following order: 1,4-phenylenediamine > 1,2-phenylenediamine which runs reverse to the order of inhibition and is in good agreement with the results obtained from chemical and electrochemical methods. Chapter Ш G (Chemical Structure and Corrosion Inhibition). from study of the chemical structure the metal and corrosion inhibition note that, 1,4-phenylenediamine compound has a higher protection efficiency than 1,2-phenylenediamine, o-anisidine and 4-nitro-ortho-phenylenediamine compound , this is attributed to steric hindrance between the two NH2 groups in ortho position to each other in 1,2-phenylenediamine, o-anisidine and 4-nitro-ortho-phenylenediamine , molecule. Also, 1,4-phenylenediamine and 1,2-phenylenediamine compound has a higher protection efficiency than o-anisidine and 4-nitro-ortho-phenylenediamine because that o-anisidine and 4-nitro-ortho-phenylenediamine contains ( OCH3, NO2) groups respectively, this is attributed to electron-withdrawing of benzene ring and the copper metal. The order of decreasing inhibition efficiency of aromatic diamine compounds is: 1,4-Phenylenediamine > 1,2-Phenylenediamine > o-anisidine > 4-nitro-ortho-phenylenediamine .