الفهرس 
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Abstract
The corrosion is a great problem, which faced the world, we can
not hide this problem from our live but we can reduce it by several
methods as the environment need. This work discusses the corrosion
inhibition of carbon steel in 1 M HCl solution by Cationic surfactants
This work contains three chapters:-
Chapter 1: ”Introduction”
Which including that:-
An introduction about surfactant (definition, classification and
applications), An introduction about corrosion (definition, forms and
inhibition), A literature survey on the previous studies on corrosion
inhibition of carbon steel in aqueous solution is given.
Chapter 2: ”Materials and experimental techniques”
The experimental part includes complete description of synthesis
of inhibitors used, preparation of solution, carbon steel electrode
pretreatment, electrolytic cell working procedures, weight loss
measurements.
Chapter3: “Results and discussion”
This chapter included the following parts:-
1-Preparation of surfactants
The target compounds were prepared through two steps. In the
first step, the ester compounds were synthesized by reaction of triethanol
amine and different fatty acids (dodecanoic acid, tetradecanoic acid and
hexadecanoic acid), the molar ratio is 1:1, the reaction carry out in
presence of xylene as solvent and p-toluene sulfonic acid as dehydrating
agent, the product is (2-hydroxyethyl)amino)ethyl alkyl ester. The
reaction was completed when the water was removed from reaction
system and its concentration was 1 mol. The reaction mixture was
distilled under vacuum to remove the solvent.
In the second step, the end products were prepared by a reaction
of hexadecyl bromide with appropriate amount of 2-(bis(2-
hydroxyethyl)amino)ethyl alkyl ester in the molar ratio of 1:1 to produce
2-(alkylcarbonyloxy)ethyl)hexadecyl-bis(2-hydroxy-ethyl)ammonium;
bromide .The reactants were allowed to reflux in ethanol for 12 h. Then
the reaction mixture was left to cool to room temperature.
2- Characterization of the synthesized surfactants
The chemical structures of the prepared surfactants were
confirmed by the FTIR and 1HNMR spectra. All prepared compounds
have the same signals. The only difference between the signals of these
compounds is the signal intensity of methylene proton.
3-The prepared compounds were tested as corrosion inhibitors using
three techniques.
a) Weight loss measurements
The data reveals that, the inhibition efficiencies for all prepared
cationic surfactants compounds increases with increasing its
concentration. The inhibition efficiencies decrease in the temperature
rang (30-40ºC) and increase in the temperature rang (40-50ºC).
The percentage inhibition efficiency increases by increasing the
alkyl chain in the surfactant. The values of inhibition efficiency obtained
from the weight loss measurements are in good agreement with those
obtained from potentiodynamic polarization method and electrochemical
impedance spectroscopy (EIS).
The values of activation energy (Ea) were calculated from
Arrhenius equation. The data reveals that, the activation energy decrease
in the presence of cationic surfactants which indicates that chemical
adsorption (strong adsorption of surfactant molecules on the metal
surface).
The change in enthalpy and entropy of activation values (ΔHo,
ΔSo) were calculated from the transition state theory
The adsorption of these cationic surfactants on the carbon steel
surface obeys the Langmuir adsorption isotherm.
Thermodynamic parameters for adsorption process such as free
energy (ΔGo
ads) enthalpy (ΔHo
ads) and entropy (ΔSo
ads) for the prepared
surfactants were determined. The negative values of ΔGo
ads indicating
that, the adsorption of surfactants on the metal surface is spontaneous
process. All prepared surfactants have positive sign of ΔHo
ads indicating
that the adsorption of prepared surfactants on the carbon steel surface in
1M HCl solution is endothermic process. The positive sign of ΔSo
ads
attributed to the increase of disorder due to the adsorption of only one
surfactant molecule by desorption of more water molecules.
b) Surface tension (γ)
The data reveals that the values of surface tension decreases as
the activity (concentration) of cationic surfactants increases. The values
of effectiveness (ΠCMC), Maximum surface excess (Tmax) and the
minimum surface area (Amin) were calculated. The data reveals that the
most effective surfactant is one that gives the greater lowering in surface,
by increasing the hydrophobic character of the cationic surfactants shifts
Γmax to lower concentrations and the minimum area per molecule at the
aqueous solution/air interface increases with increasing length of the
hydrophobic part. Specific conductivity (K) measurements were
performed in order to evaluate the CMC and the degree of counter ion
dissociation, β. The data reveals that the degree of dissociation increases
by increasing carbon chain length.
The values of standard free energy (ΔGo
mic) were calculated. The
data reveals that the standard free energies of micellization for the
synthesized surfactants are always negative, indicating that the
micellization is a spontaneous process
3- Antimicrobial Activity
Most of the synthesized compounds were evaluated for their
antimicrobial activity using the agar diffusion technique (Cooper, 1972).
1 mg/ml solution in dimethyl formamide was used. The tested organisms
were Gram-negative bacteria (Escherichia coli, NCTC-10416 &
Pseudomonas aerogenasa, NciB9016), Gram-positive bacteria (Bacillus
subtilis, NCIB-3610 & Staphylococcus aureus, NCTC-7447) and fungi
(Aspergillus niger, ferm-BAM C-21) and unicellular fungi as Candida
albicans. The bacteria and fungi were maintained on nutrient agar
medium and Czapeks Dox agar medium, respectively. DMF showed no
inhibition zones. The agar media were inoculated with different test
microorganism. After 24 hrs. of incubation at 30°C for bacteria and 48
hrs. of incubation at 28°C for fungi, the diameter of inhibition zone (mm)
was measured.