الفهرس 
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Abstract
The corrosion is a great problem, which faced the world, we cannot hide this problem from our live but we can reduce it by several methods
as the environment need. This work discus the corrosion inhibition of
carbon steel in 1M HCl solution in precence of expired pharmaceutical
drugs .
This thesis includes three chapters:-
A- Introduction
An introduction about inhibitors (definition and classification), an
introduction about corrosion (definition, forms and inhibition), and a
literature survey on the previous studies on corrosion inhibition of carbon
steel in aqueous solution is given.
B- Materials and experimental techniques
The experimental part includes complete description of preparation
of solution, carbon steel electrode pretreatment, and electrolytic cell
working procedures, weight loss measurements, and electrochemical
measurements e. g. potentiodynamic polarization and A.C. impedance
techniques.
C- Results and discussion
This chapter illustrate the compounds were tested as corrosion
inhibitors using some techniques.
First: Weight loss measurements
The data reveals that, the inhibition efficiencies for all used expired
drugs compounds increases with increasing its concentration. The
Summary
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inhibition efficiencies decrease with increase the temperature rang (25-
55ºC) except compound II.
Second: Open circuit potential measurements (OCP)
The potential of the carbon steel electrodes immersed in the 1M
HCl were measured (against a standard saturated calomel electrode, SCE,
placed in the same compartment) as a function of immersion time in
absence and presence of different concentrations from expired drugs.
Third: Potentiodynamic polarization measurements
The data reveals that, all used expired drugs slightly shifted Ecorr to
more negative potential and also the values of Icorr decreases including
both anodic and cathodic Tafel slopes βa, βc in the presence of the used
expired drugs and this confirms that compounds act as mixed type
inhibitor. The inhibition efficiency increased with increment of inhibitor
concentrations. This fact suggests that the inhibitor molecules may first
be adsorbed on the steel surface and cover some sites of the electrode
surface.
Fourth: Electrochemical impedance spectroscopy (EIS)
The data reveals that the increase of polarization resistance and
decrease of the pseudo capacity with increasing inhibitor concentration
indicates that these compounds have the ability to inhibit the corrosion
rate of carbon steel in according to adsorption mechanism (formation of a
surface film).
The percentage inhibition efficiency increases by increasing
concentration of inhibitors (expired drugs). 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).
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The values of activation energy (Ea) were calculated from Arrhenius
equation. The data reveals that, the activation energy decrease in the
presence of used expired drugs which indicates that physical adsorption
except compound II is chemical adsorption (strong adsorption of
compound molecules on the metal surface).
The change in enthalpy and entropy of activation values (ΔH*, ΔS*) were
calculated from the transition state theory. The adsorption of these
compounds on the carbon steel surface obeys the Langmuir adsorption
isotherm.
Thermodynamic parameters for adsorption process such as free energy
(ΔGads) enthalpy (ΔHads) and entropy (ΔSads) for the used expired drugs
were determined.
The calculated ΔGads negative in values which indicates that the
adsorption mechanism of the expired drugs on carbon steel in 1 M HCl
solution is a mixed from physical and chemical adsorption and the
adsorption of inhibitors on the metal surface are spontaneous process. All
used expired drugs have positive sign of ΔHads indicating that the
adsorption of expired drugs on the carbon steel surface in 1M HCl
solution is endothermic process. The positive sign of ΔSads attributed to
the increase of disorder due to the adsorption of only one inhibitor
molecule by desorption of more water molecules.
Fifth: Scanning electron microscope (SEM)
The data reveals that, the surface of carbon steel was strongly
damaged in absence of used expired drugs, However in the presence of
these compounds (I-V) the surface of steel is free from pits and it is
smooth. Such surface indicate that a good protective film present on the
steel surface and also confirms the highest efficiency of the used expired
drugs at 500 ppm concentration.
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Chapter 4: “References”
This chapter includes the references which can used in the present
work and we can arrange in very simple and include more than 150
refresh references.