الفهرس 
Introduction and Aim of the WorkOnly 14 pages are availabe for public view
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Abstract
The corrosion problem is a great problem, which faced the world from the last years until now, we cannot hide this problem from our life but we can reduce “inhibit” it in the metals and alloys by several methods as the environment need. This work discusses the corrosion of Al-Si alloy in
0.1M HCl. The aim of this work contains three main chapters.
The first chapter:
Deals with the introduction, which includes corrosion theories, types of corrosion, corrosion protection, literature survey on corrosion behavior of Al-Si alloy and in aqueous solutions and the aim of this study.
The second chapter:
It includes the experimental techniques, preparation of the used solutions, the chemical composition of the investigated compounds, the instruments, the procedures used for the corrosion measurements such as a weight-loss and electrochemical techniques.
The third chapter
Deals with the results obtained and their discussion and is divided into three sections:
Section 1:
Evaluation of the inhibitor efficiency by weight loss method in the presence and absence of the used pharmaceutical compounds in 0.1M HCl. This revealed that the inhibitor efficiency increases with increasing the concentration of inhibitor. from these studies, the order of inhibition efficiency of investigated pharmaceutical compounds in 0.1M HCl is found to be:
Metronidazole (A) > Flubendazole (B) > Albendazole (C)
These investigated pharmaceutical compounds obey Temkin isotherm showing that the inhibition is by adsorption. The degree of surface coverage (θ) for the inhibitors on the metal surface increases with increasing the concentration in the corrosive medium. The action of the inhibitors in the aggressive acid was assumed to be due to their adsorption at the metal /solution interface. The effect of temperature on the corrosion inhibition of Al-Si alloy in 0.1M HCl was determined over the temperature at 30 and 50oC using weight loss measurements. The rate of corrosion increases with increasing the temperature together with decrease in inhibition efficiency, indicating that the inhibition occurs through physical adsorption of the additives on Al-Si surface. Thermodynamic functions of activation were calculated.
Section 2:
Potentiodynamic polarization measurements were carried out for Al-Si alloy in 0.1M HCl in the absence and presence of different concentrations of the investigated pharmaceutical compounds. The polarization curves indicated that these inhibitors influence both cathodic and anodic processes. The corrosion rate decreased with increasing the concentration of these inhibitors with increase in inhibition efficiency. The order of decreasing inhibition efficiency for these organic inhibitors is:
Metronidazole (A) > Flubendazole (B) > Albendazole (C)
AC impedance spectroscopy measurements were carried out for Al- Si alloy in 0.1M HCl in the absence and presence of different concentrations of the investigated pharmaceutical compounds under charge transfer control.
from the impedance data, we conclude that:
The value of charge transfer resistance (Rct) increases with increase in the concentration of the inhibitors and this indicates a decrease in the corrosion rate.
i. The value of double layer capacitance (Cdl) decreases by increasing the inhibitor concentration. This is due to the adsorption of these compounds on the electrode surface leading to a film formation on the Al-Si alloy surface, suggesting an increase of the surface coverage (ɵ) of the inhibitor.
ii. The inhibition efficiency (%IE) obtained from EIS measurements are close to those deduced from weight-loss and polarization techniques.
Electrochemical frequency modulation measurements (EFM) were used as a rapid and non-destructive technique for corrosion rate measurements. It was carried out for Al-Si alloy in 0.1M HCl in the absence and presence of different concentrations of the investigated organic compounds.
Corrosion current densities (icorr) obtained with the EFM was in good agreement with those obtained from weight-loss, polarization and EIS methods.
Section 3:
Surface examination of Al-Si alloy includes the following:
1. SEM analysis showed that the inhibition of the investigated pharmaceutical compounds was adsorbed on the metal surface forming a thin layer by which metal was protected from corrosion.
2. AFM spectroscopy used for investigation the roughness of Al-Si alloy surface were given in nonexistence and existence of compounds.
3. The metal specimen was analyzed by ATR- FTIR technique. Chemical bonds and functional groups in a molecule had been recognized by generate an infrared absorption spectrum.
The order of decreasing the inhibition efficiency of the investigated compounds in 0.1M HCl solution was:
Metronidazole (A) > Flubendazole (B) > Albendazole (C)
Conclusion:
The electrochemical measurements and non-electrochemical calculations support the assumption that corrosion inhibition primarily takes place through adsorption of the inhibitors on Al-Si alloy surface. Agreement among these different independent techniques indicates the validity of the obtained results.
The thesis contains scientific research a summary in Arabic and another in English and references.