الفهرس 
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Abstract
English Summary
Carbon steel was considered that one of the most important metals which find extensive domestic and industrial applications. This was because it was characterized by low cost, high density, excellent electrical and thermal conductivities, good appearance, recyclability, formability, durability and high ductility. CS is the extended metal utilized in industrial purpose, Army equipment, building and more in manufacturing of installations for petroleum, fertilizers and other industry. So the protection of C-steel in aqueous solutions is universal request, economic, environmental, and aesthetical important . The use of inhibitor is more effective way to reduce the corrosion of CS. The organic assembled was commonly utilized as corrosion inhibitors as it contains heteroatom such as O, N, P, S, and heavy metals. The surfactant adsorption by heterocyclic compounds on the surface of metal can markedly exchange the corrosion- resisting assets of the metal and so the revision of the relations among the adsorption and corrosion protection is of pronounced important. Heterocyclic compounds have exposed a good protection efficiency for iron in both HCl and H2SO4 solutions. Green inhibitors like natural products from plant extracts and substances from other renewable sources are of the interest of the researchers who are interested in “green chemistry” or “eco-friendly” technologies such as azo and shiff compounds.The aim of the present work is to study the corrosion of carbon steel in 1 M HCl using azo and shiff compounds such as 4-((4-formyl-3-hydroxyphenyl) diazenyl)-3-hydroxynaphthalene-1-sulfonic acid, (E)-2-hydroxy-5-((4-sulfophenyle) diazenyl)benzoic acid, (E(4-((4-hydroxynaphthalen-1-yl)diazenyl)benzenesulfonic acid, 4-((2-hydroxybenzylidene) amino) benzenesulfonic acid and 4-(benzylideneamino)benzenesulfonic acid .The thesis contains three chapters:Chapter (I)is concerned with an introduction about the carbon steel metal, its occurrence, its electrochemical reactions in aqueous solutions, theories of corrosion, types of corrosion inhibitors and the usage of naturally occurrence substances as corrosion inhibitors. Moreover, the chapter contains a literature survey on corrosion behavior of carbon steel in aqueous solutions.Chapter (II) deals with experimental part, which includes a description of the working procedures, preparation of solutions, electrode treatment, electrolytic cell and electrochemical measurements. This chapter also show the procedure of synthesis of 4-((4-formyl-3-hydroxyphenyl)diazenyl)-3-hydroxynaphthalene-1-sulfonic acid(compound IA), (E)-2-hydroxy-5-((4-sulfophenyle) diazenyl) benzoic acid (compound IIA), (E(4-((4-hydroxynaphthalen-1-yl)diazenyl)benzenesulfonic acid(compound IIIA), 4-((2-hydroxybenzylidene)amino)benzenesulfonic acid (compound IB) and 4-(benzylideneamino)benzenesulfonic acid (compound IIB).Chapter (III)This chapter presents the Results and discussion of the data obtained. This chapter is divided into four sections as follows: Section 1:Contains the result and discussion of Weight loss measurements for carbon steel in 1M HCl solution containing different concentrations of inhibitors at room temperature. The data reveals that, the inhibition efficiencies for all prepared azo and shiff compounds increases with increasing its concentration. Section 2:Contains the result and discussion of Potentiodynamic polarization measurements for carbon steel in 1M HCl solution containing different concentrations of inhibitors at room temperature The corrosion potential does not affected by the addition of the examined compounds.i.The corrosion rate decreases and the inhibition efficiency increases with increasing additive concentration. Upon increasing the additive concentration in the bulk solution the number of molecules adsorb on carbon steel surface increases leading to an increase in the inhibition efficiency.ii. Both anodic and cathodic Tafel constants change slightly upon addition of increasing concentration of the additive. This result indicates that the addition of the tested compounds does not affect the mechanism of carbon steel dissolution. Moreover, these findings lead to conclusion that the additives act as mixed type inhibitors. This type of inhibitors acts by adsorption on both anodic and cathodic sites on the metal surface and thus retards both the anodic and cathodic reactions. This behavior results in decreasing the corrosion rate of the metal.Section 3:Contains the result and discussion of Potentiodynamic polarization measurements for carbon steel in 1M HCl solution containing four high concentration at different temperature. The data reveals that, the prepared the tested compounds act as mixed type inhibitor also the inhibition efficiency increased with inhibitor concentration increment and the inhibition efficiency decrease with increase of temperature using the tested compounds. The values of activation energy (Ea), the enthalpy of activation (ΔH*) and the entropy of activation (ΔS*) were calculated. The adsorption of isotherm for these surfactants on carbon steel surface followed Langmuir adsorption isotherm at room temperature.Section 4: Contains the result and discussion of electrochemical impedance spectroscopy (EIS) measurements for carbon steel in 1 M HCl solution containing different concentrations of inhibitors at room temperature. The data reveals that, the increase of polarization resistance with increasing inhibitor concentration indicates that these compounds have the ability to inhibit the corrosion rate of carbon steel in according to adsorption mechanism (formation of a surface film).All the used techniques showed that, the inhibition efficiencies values, in acidic solution, decreases in the following order:>(IA) (IIA) > (IIIA) and (IB) > (IIB).