الفهرس 
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Abstract
Summary
The thesis consists of three chapters. Chapter I is the introduction, Chapter II represents the experimental techniques and Chapter III contains the experimental results besides the analysis, manipulation and the discussion of the data.
Chapter I: In this chapter, the introduction was given which deals with the following fields of interest: Composition and properties of copper and its alloys, Types of copper alloys, Electrochemical nature of corrosion, Corrosion resistance of copper and its alloys, The potential-pH diagram of copper, The electrical double layer in aqueous solution, Potential of Zero charge, The electrochemical techniques for measuring corrosion rates, Corrosion inhibitors and their classification, Adsorption isotherms, Corrosion forms of copper and its alloys, and literature survey on corrosion behavior of copper and its alloys. The aim of the work was also given in this part.
Chapter II: The main contents of this chapter were the detailed description of the electrochemical cell, the electrodes and design of the working electrode, and the electrochemical techniques used in the present investigation, the preparation of the aqueous stock and test solutions, preparation of the plant extracts , and the main chemical constituents of the plant extracts.
Chapter III: This chapter represents the validity of the potentiodynamic polarization and electrochemical impedance spectroscopy techniques for measuring the corrosion rate by Analysis of Variance (ANOVA) that enables the calculation of the mean and standard deviation of the data. The simple correlation, linear regression analysis and factor analysis for measuring the relationships between the variables affecting the corrosion rate and calculating the correlation coefficient (R2) for the linear fitting of the data of the plant extracts to Langmuir adsorption isotherm, Kinetic-thermodynamic model and Flory-Huggins adsorption isotherm. When the values of (R2) ≥ 0.95, the linear fits are acceptable.
The evaluation of inhibition efficiency of Damsisa, Lupine and Camphor as corrosion inhibitors for copper in 0.5M H2SO4, 1.0M HNO3, 1.0M H3PO4, 0.5M Na2SO4 showed that:
•The polarization curves of copper in aqueous solutions containing different concentrations of Damsisa, Lupine and Camphor extracts showed that the extracts act as mixed-type inhibitors as they shift both the anodic and cathodic polarization curves to higher voltages, so they decrease the corrosion current density, icorr. Furthermore, Tafel behavior in anodic curves indicated that the oxidation reaction of copper is mainly controlled by charge transfer process while the cathodic reaction of oxygen reduction is mainly controlled by diffusion of oxygen gas from the bulk solution to copper surface.
•The Nyquist plots of the complex impedance showed that the size of semicircles increased with increasing the concentration of Damsisa, Lupine and Camphor extracts confirming that they act as corrosion inhibitors for copper. Nyquist plots were characterized by capacitive loops at high frequency followed with diffusion tails indicating that the corrosion is of mixed kinetic and mass transport mechanism and is under activation and diffusion control.
•The data of the corrosion rate represented in the corrosion current density ( icorr.) and the reciprocal of charge transfer resistance (1/Rct) showed that phosphoric acid is the most aggressive aqueous solution for copper while sodium sulphate solution is the least aggressive solution.
•In all of the investigated solutions, the decrease in the values of Qdl on increasing the inhibitor concentration indicating that the increase of the thickness of electrical double layer and suggesting that the extracts inhibited the corrosion of copper by their adsorption at copper/solution interface.
•the linear fitting of the data of the plant extracts to Langmuir adsorption isotherm indicated that the adsorption process occurred reversibly and rapidly and there is no lateral interactions between the adsorbed inhibitor molecules. The linear fitting of the data of the plant extracts to the Kinetic-thermodynamic model indicated the corrosion experiment carries out all features of kinetic and thermodynamic implications. While the linear fitting of the data of the plant extracts to Flory-Huggins adsorption isotherm indicated that the adsorption process of the inhibitor is a simple substitutional process in which the inhibitors occupies active sites (1/y) on copper surface and displace (x) water molecules.
The values of the binding constant (K) for adsorption of damsisa, lupine and camphor extracts showed that the inhibition efficiency of the extracts followed the order: Lupine Camphor Damsisa.