الفهرس 
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Abstract
Surface active agents are considered as important compounds which have important applications in various industrial fields. In addition to participate in the formulation of emulsions and phase transfer catalysis, surface active agents are used as corrosion inhibitors for different metals in the corrosive media
As the result of the integrated usage of the surface-active agents in several industrial fields, their improvement was urgent to synthesize new types which characterized by higher efficiency in their applications and to decrease the used dose. The unique improvement of the surface-active agents was synthesized triquaternary ammonium trimeric cationic salts (made up of three amphiphilic moieties connected by a spacer) and monomeric cationic salts to improve their adsorption at the different surfaces. That increased their efficiency as corrosion inhibitors considerably.
In this thesis, three series of triquaternary ammonium trimeric cationic salts and two series of ammonium monocationic salts yielding five products acting as surface active agents were synthesized and then the chemical structures of the synthesized triquaternary ammonium trimeric cationic surfactants were corroborated using microelemental analysis, Fourier Change Infrared Spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance (1HNMR) Spectroscopy.
The prepared surfactants were evaluated as corrosion inhibitors for carbon steel in the deep oil wells formation water by various electrochemical techniques such as: potentiodynamic polarization measurements and electrochemical impedance measurements (EIS). In addition, the theoritical calculations and molecular dynamic simulations are used to study the corrosion inhibition efficiency of the prepared tricationic and monocationic surfactants. The surface morphology of the carbon steel alloy in the deep oil wells formation water in the absence and presence of the selected prepared compounds were determined using atomic force microscopy (AFM) technique. Data about the explanation of the chemical structure showed the purity and precision of the preparation compounds’ experimental synthesis. The main conclusions of this work may be stated in the following points:
Trimeric cationic aliphatic surfactants have been prepared by esterification reaction followed by a quaternization reaction, also monocationic aliphatic surfactants have been prepared by quaternization reaction and then investigated through micro elemental analysis, FTIR and 1HNMR spectroscopy.
The prepared trimeric aliphatic cationic surfactants act as the effective inhibitors for the corrosion of S90 type carbon steel in formation water, and the corrosion inhibition efficiency increase in the following order; AED ˃ AEO ˃ AEB. Also the prepared monocationic aliphatic surfactants increase in the following order; PC12 ˃ DEC12.
Tafel curves indicated that the prepared trimeric aliphatic cationic surfactants and monocationic aliphatic surfactants suppresses both anodic and cathodic processes and thus act as mixed-type inhibitors.
The results of EIS measurements revealed that the value of both Rct and IE % tend to increase and the value of Cdl tend to decrease upon increasing the inhibitors dosage. This data can be ascribed to the increase of the thickness of the electrical double layer.
The adsorption of the prepared trimeric cationic surfactant and monocationic aliphatic surfactants on the surface of S90 carbon steel obeyed Langmuir adsorption isotherm and blocking of its active sites. The negative sign of 〖ΔG〗_ads^° showed the adsorption process was spontaneous. The values of free energy of adsorption indicate that the adsorption was mixed physical and chemical adsorption.
Surface analysis tools such as AFM indicated that the trimeric cationic surfactant inhibitor molecules produced a good protective film on the S90 carbon steel surface that separates the S90 surface from the corrosive medium.
Quantum chemical calculations indicated that the inhibition efficiency of the inhibitor raised with the incrase in E_HOMO and declining in the energy band gap (∆E). The data obtained from quantum chemical calculations are in good agreement with the electrochemical experimental results.
The adsorption of these trimeric cationic surfactants on the carbon steel surface can occur directly via donor – acceptor interactions between the lone pair of electrons present on heteroatoms (O, N) of the inhibitors (as electron donor) and the unoccupied d-orbitals of Fe on carbon steel surface (as electron acceptor), or by electrostatic interaction between the positive charge in the triquaternary nitrogen atom on the aliphatic trimeric cationic surfactant molecules and the negative charged Cl− ions on S90 carbon steel surface.