الفهرس 
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Abstract
Pipelines play an extremely important role through the world as a means of transporting gases and liquids over long distances from their
sources to ultimate consumers. So that corrosion problems exist in the oil industry at every stage of production from initial extraction to refining and storage prior to use requiring the application of corrosion inhibitors. It has been reported that corrosively is related to the nature of formation water accompanying the oil production process. One of the most economic methods is the application of corrosion inhibitors. The
surfactant inhibitors have many advantages such as high inhibition efficiency, low price, low toxicity and easy production. The activity of these surfactants very much depends on their types, compositions and concentrations; in addition to the environmental factors, such as (temperature, pressure, solvents and additives). So, this work aims to synthesis of a new family of nonionic surfactants based on tolyltriazole and evaluation their inhibition efficiency on the carbon steel corrosion in oil wells formation water. This work includes three main parts:
THE FIRST PART:
Synthesis of Compounds Used Condensation reactions of tolyltriazole with citric acid were carried out. To the formed product poly ethylene glycol (PEG) with different molecular weight (Mol.Wt. 400, 3000, 4000 and 6000) were added to
give four nonionic surfactants (I-IV). The purity of the products was checked by FTIR and elemental analysis.
THE SECOND PART:
Study the Surface Activity of the Synthesized Surfactants Surface activity was studied for the synthesized nonionic surfactants by setting some properties such as surface tension (γ),
critical micelle concentration (CMC), maximum surface excess concentration (Гmax) and minimum surface area per molecule (Amin).
THE THIRD PART:
Evaluation of the Prepared Surfactants as Corrosion Inhibitors Using Different Techniques
1. Weight Loss Studies The weight losses of carbon steel in formation water (in mg cm-2)
with and without the addition of surfactant inhibitors were determined at different immersion times. It was found that the inhibition efficiency
of all these compounds increases with increasing its concentration. The maximum inhibition efficiency for each compound was achieved at 450
ppm and further increase in concentration did not cause any appreciable change in the performance of the inhibitors. The percentage inhibition
efficiency was found to be in the following order:
IV > III > II > I
The data obtained from weight loss technique have been tested with several adsorption isotherms. Langmuir adsorption isotherm was found to fit well with our experimental data.
2. Different Electrochemical Measurements
A. Open Circuit Potential Measurements (OCP)
The variation of the OCP of the carbon steel electrode as a function of the period of exposure in the absence and presence of various concentrations of the surfactants were measured against a saturated calomel electrode (SCE). It was found that the potential of carbon steel electrode immersed in formation water tends toward more negative potential firstly, giving rise to short step. By addition of inhibitor molecules to the aggressive medium produces a slightly
positive shift in Ecorr due to the formation of a protective film on the carbon steel surface.
B. Potentiodynamic Polarization Measurements
The results of potentiodynamic polarization for carbon steel dissolution in oil wells formation water with and without different concentrations of inhibitors have been investigated. The polarization curves indicated that both anodic metal dissolution and cathodic reduction reactions were inhibited when the surfactants added to the
formation water, where the Tafel lines are shifted to more negative and more positive potentials with respect to the blank curve by increasing the concentration of the surfactant inhibitor. This behavior indicates that the undertaken additives act as mixed type inhibitors. It was found that
the inhibition efficiency increased with increasing inhibitor concentration.
C. Electrochemical Impedance Spectroscopy Measurements (EIS) The corrosion behavior of carbon steel immersed in oil wells formation water in the presence and absence of the synthesized
surfactants was investigated by EIS after immersion in solutions for 4 h.
The results of EIS indicate that the increase of surfactant concentrations leads to increase the charge transfer resistance (Rt) and decrease the
double layer capacitances (Cdl), which indicates that these compounds act as corrosion inhibitors through adsorption on the surface of the
carbon steel.
It was found that the data obtained from the electrochemical techniques are in good agreement with that obtained from weight loss technique.
Since, the percentage inhibition efficiency was found to be in the following order:
IV > III > II > I
3. Scanning Electron Microscopy (SEM)
The SEM results, indicated that the carbon steel sample placed in the oil wells formation water for 60 days in the absence of inhibitor show highly damage to the surface, while the sample placed in the solution in the presence of 450 ppm of the inhibitor (IV) did not significantly affected as a result of the inhibitor layer formed on the
carbon steel surface.
4. Energy Dispersive Analysis of X-Rays (EDX)
The results of EDX, reveal that the curve of iron atom (Fe) in the presence of 450 ppm of the inhibitor (IV) less than in the absence of
the inhibitor, which indicates that the surfactant inhibitor layer formed on are strongly attached to the carbon steel surface, and thus leads to a
high degree of inhibition efficiency.
At the end of the thesis, the relation between the surface properties of the investigated surfactants and their corrosion inhibition efficiency IE % were studied.