الفهرس 
List of the origin used chemicalsOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
values of the cationic surfactants in 1M The work discusses the corrosion inhibition of carbon steel metal in 1M HCl solution and formation water by different synthesized cationic surfactants I(4N), II(4N) and IV(4N). In this work, the inhibition effects of those compounds have been studied by several experimental methods.
This work contains three chapters:
Chapter 1:”Introduction”
This chapter includes a general introduction about corrosion (definition, the economic cost, forms, factors, prevention and types of inhibitors) and surfactants (definition, classification and applications).
Chapter 2: ”Materials and experimental techniques”
The experimental part includes complete description of chemicals used, preparation of solutions, metal composition, synthesis of cationic surfactants and description of their application as the following:
• Synthesis of new cationic surfactants
The desired cationic surfactants were synthesized through two main steps, the first step was formation of the main Schiff base by reaction N1,N1’-(ethane-1,2-diyl)bis(ethane-1,2-diamine) with isonicotinaldehyde while the second step was quaternization reaction of the prepared Schiff base with different number of dodecyl bromide compounds to obtain the desired cationic surfactants.
• Confirmation the chemical structure of prepared Schiff base and cationic surfactants using FTIR, 1HNMR and Mass spectroscopes.
• Evaluation the inhibition efficiency for the synthesized cationic surfactants as corrosion inhibitors for carbon steel pipelines in both 1M HCl solution and formation water by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques.
• Determination of activation and adsorption thermodynamic parameters of the cationic surfactants on the carbon steel surface in 1M HCl solution and formation water.
• Determination of synergistic effect between KI, ZnCl2 and the cationic surfactants in formation water.
• Determination of the surface parameters of the synthesized cationic surfactants.
Chapter 3: ”Results and discussion”
This chapter included the following parts:-
1. Characterization of the synthesized Schiff bases:
The chemical structure of the synthesized cationic surfactants was confirmed by spectroscopy analysis include: FTIR, 1HNMR, and Mass Spectra.
2. Evaluating of the synthesized cationic surfactants as corrosion inhibitors for carbon steel in 1M HCl solution and formation water by
2.1. Weight loss measurements
The prepared compounds I(4N), II(4N) and IV(4N) were tested as corrosion inhibitors for carbon steel in 1M HCl solution at four different temperatures 25, 40, 55 and 70oC and in formation water at 25oC only. The data revealed that, the inhibition efficiency of the synthesized cationic surfactants increases with increasing the cationic surfactant concentration in both media, also it was found that inhibition efficiency decreases with increasing the temperature in 1M HCl.
Synergistic effect between KI, ZnCl2 and cationic surfactants in formation water was studied. The experimental data showed that, after adding various concentrations of KI and ZnCl2 to the cationic surfactants at 25 oC, the inhibition efficiency increases by increasing the concentration of inorganic salts. This behaviour indicating that, the synergism phenomenon exists between cationic surfactant and KI or ZnCl2 leading to increasing the inhibition efficiency
2.2. Potentiodynamic polarization measurements
The data indicated that:-
The presence of the synthesized cationic surfactants in both 1M HCl solution and formation water slightly shifted the corrosion potential (Ecorr) to both negative and positive directions. This indicates that the synthesized cationic surfactants acted as a mixed type inhibitor
For all synthesized cationic surfactants,(icorr) decreased whereas (ηp) increased with increasing the inhibitor concentration. This could be related to the adsorption of the inhibitor over the cathodic and anodic active corroded surface. The increase in corrosion inhibition efficiency of the studied surfactant indicated that the synthesized cationic surfactant had efficient inhibitive properties for the metal surface.
2.3. Electrochemical impedance spectroscopy (EIS)
In both 1M HCl solution and formation water, the data showed that the increase of charge transfer resistance (Rct) and decrease of the pseudo capacity, (Cdl), with increasing the inhibitor concentration indicated that, these compounds have the ability to inhibit the corrosion rate of carbon steel according to adsorption mechanism (formation of a surface film). It was found that the order of the inhibition efficiencies of the cationic surfactants decrease in the following arrangement:
IV(4N) > II(4N) > I(4N)
and these results were in good agreement with those obtained from weight loss and potentiodynamic polarization methods
3. Thermodynamic parameters
3.1. Adsorption thermodynamic parameters
The adsorption of the synthesized cationic surfactants on the carbon steel surface in 1M HCl solution and formation water obeyed the Langmuir adsorption isotherm. Thermodynamic parameters for adsorption process such as free energy (∆Goads), enthalpy (∆Hoads) and entropy (∆Soads) for the synthesized cationic surfactants were determined.
The calculated ∆Goads values are up to -40 kJ mol-1 in 1M HCl and -36 kJ mol-1 in formation water which indicates that adsorption process of inhibitors on the metal surface is mixed physical and chemical adsorption. Also the negative values of ∆Goads indicated that the adsorption of inhibitors on the metal surface is a spontaneous process.
The negative sign of ∆Hoads HCl indicated that the adsorption of inhibitor molecules is an exothermic process.
The positive sign of (∆Soads) in 1M HCl is attributed to the increase of disorder due to the adsorption of only one cationic surfactant molecule by desorption of more water molecules.
3.2. Activation thermodynamic parameters
The values of activation energy (Ea) were calculated from Arrhenius equation in 1M HCl solution. The data indicated that, the activation energy increases with the increase in the cationic surfactant concentration, which further confirm ηw decreases with increase in temperature.
Data of the activation parameters (ΔH* and ΔS*) revealed that the dissolution reaction of carbon steel in 1M HCl in the presence of the inhibitors were less than those in the absence of inhibitors (blank). The positive signs of the enthalpy (ΔH*) reflected the endothermic nature of the steel dissolution process and indicated that the dissolution of steel was difficult. The entropy values of activation are large and negative and this implies that the activated complex in the rate-determining step represents association rather than dissociation.
4. The surface active properties of the prepared surfactants in both 1M HCl solution and formation water
The data showed that the linear decrease in surface tension was observed with an increase in the surfactants concentration up to specific concentration called (Ccmc), beyond which no considerable change was noticed. The values of effectiveness (πcmc), maximum surface excess (Γmax) and the minimum surface area (Amin) were calculated.
The Ccmc obtained data demonstrated that, the increase in the number of the hydrocarbon chains leading to lowering Ccmc values of prepared cationic surfactants, this is attributed to the increase in the hydrophobicity and the decrease in hydrophilicity, thus Ccmc decreases. Also, it was found that, Amin values of the prepared cationic surfactants increase by increasing the carbon chains number and this could be due to the increase in molecular structure of cationic surfactant molecule in solution. The effectiveness values (πcmc) increases with increasing number of the hydrocarbon chain, and these phenomena could be due to the hydrophobicity of surfactants in aqueous media.
The values of standard free energy for micellization (ΔGomic) were calculated. The data showed that the standard free energies of micellization for the synthesized surfactants are always negative, indicating that the process are spontaneous.