الفهرس 
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Abstract
English summary
Carbon steel is a very important alloy used in industry so we tried to decrease its corrosion rate in 1.0M HCl using some surfactant inhibitors named; (N,N,N-trimethyl-3-tetradecanoamidopropan-1-ammonium methyl sulfate), (N,N,N-trimethyl-3-hexadecanoamidopropan-1-ammonium methyl sulfate), (N-ethyl-N,N- dimethyl-3-tetradecanoamidopropan-1-ammonium iodide), (N-ethyl-N,N- dimethyl-3-hexadecanoamidopropan-1-ammonium iodide), (N,N-dimethyl-N-(3-tetradecanoamidopropyl)-1-ammonium bromide), and (N,N-dimethyl-N-(3-hexadecanoamidopropyl)-1-ammonium bromide) referred as (ACS1.1, ACS1.2, ACS2.1, ACS2.2, ACS3.1, and ACS3.2), respectively.
This work contains three chapters:
Chapter (1): Introduction
This chapter deals with an introduction about carbon steel, its occurrence, and its electrochemical reactions in aqueous solutions, theories of corrosion and types of corrosion inhibitors. Moreover, this chapter contains a literature survey of the previous works have been introduced in on carbon steel corrosion.
Chapter (2): Materials and methods
This chapter deals with an experimental work which included a description of the cationic surfactant inhibitors as the following:
Synthesis of cationic surfactants through three steps as follow:
Synthesis of (tetradecanoic and/or hexadecanoic) chloride.
Synthesis of amido-amine derivatives.
Synthesis of cationic surfactants (ACS1.1, ACS1.2, ACS2.1, ACS2.2, ACS3.1, and ACS3.2), respectively.
A description of the used instruments and detailed procedures used for determination that:
The chemical structural confirmation by using spectra tools include (FT-IR and 1H-NMR) spectra.
The critical micelle concentration (CMC) by surface tension measurements.
The corrosion measurements such as weight loss and potentiodynamic polarization methods.
Chapter (3): Results and discussion
This chapter deals with the results and its discussion and contains the following parts:
The surface active properties of synthesized cationic surfactants.
The data showed that the values of surface tension (γ) decreases as the concentration of inhibitors increased. The values of effectiveness (π_CMC), Maximum surface excess (Γ_max), and the minimum surface area (A_min) were calculated. The data showed that the most effective surfactant is one that gives the greater lowering in surface tension, by increasing the hydrophobic character of the surfactants (Γ_max) values decreased and the minimum area per molecule at the aqueous solution/air interface increased.
The values of standard free energy of micelle formation (〖∆G〗_mic^*) were calculated. The data showed that the standard free energies of micellization for cationic surfactants are always negative, indicating that the micellization is a spontaneous process.
The synthesized cationic surfactants were investigated as corrosion inhibitors using two methods:
Weight loss measurements.
Weight loss measurements were carried out for carbon steel in 1.0M HCl in the absence and presence of different concentrations of cationic surfactants at 20ºC. The obtained results show that the corrosion rate (CR) of carbon steel decreased with increasing the concentration of investigated inhibitors. The order of the inhibition efficiencies (η_w) of cationic surfactants (ACS1.1, ACS1.2, ACS2.1, ACS2.2, ACS3.1, and ACS3.2) decreases in the following arrangement:
ACS3.2 > ACS2.2 > ACS1.2 > ACS3.1 > ACS2.1 > ACS1.1
Potentiodynamic polarization method
Potentiodynamic polarization method was carried out for carbon steel in 1.0M HCl in the absence and presence of different concentrations of cationic surfactants at 30ºC. The polarization curves indicated that these compound inhibitors influence both anodic and cathodic processes without change in the corrosion potential. This means that these compound inhibitors act as mixed type inhibitors. The order of the inhibition efficiencies (η_p) of cationic surfactants (ACS1.1, ACS1.2, ACS2.1, ACS2.2, ACS3.1, and ACS3.2) decreases in the following arrangement:
ACS3.2 > ACS2.2 > ACS1.2 > ACS3.1 > ACS2.1 > ACS1.1
The obtained results show that the adsorption of synthesized surfactants on the carbon steel surface follows Temkin adsorption isotherm and there adsorption is physical in nature.
The effect of temperature on the corrosion rate of carbon steel in 1.0M HCl over the temperature range 20-60ºC in the absence and presence of the most effective concentration of cationic surfactants (ACS1.1, ACS1.2, ACS2.1, ACS2.2, ACS3.1, and ACS3.2) is s found that inhibition efficiencies (η_w) decrease with increasing temperature by weight loss method. This also, indicates that surfactant inhibitors are physically adsorbed on the carbon steel surface. Activation energies were calculated and it was found that (E_a) values for inhibited systems are higher than those for the uninhibited systems.
The activation enthalpy (〖∆H〗^*) and activation entropy (〖∆S〗^*) values were calculated. The positive values of activation enthalpy indicate endothermic nature of the reaction. The negative values of activation entropy can be attributed to the adsorption process which is accompanied by an increase in the order of the system resulting from the associated complex of inhibitor and carbon steel.