الفهرس 
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Abstract
Al-Si alloy is consider as one of the most popular alloys which occupy a vital position in our daily life owing to its wide application in automotive industry due to their strength to weight ratio which increase performance and fuel economy. The aim of the present work is to study the corrosion behavior of Al-Si alloy in 1 M HCl solution.
The results indicated that the values of corrosion rate decrease with increasing the inhibitors concentration. The order of decreased inhibition efficiency of the carbamidic thioanhydride derivatives is as follows: (1) > (2) > (3) > (4) > (5), and the order of decreased inhibition efficiency of the cyanoacetamide derivatives is as follows: (A) > (B) > (C).
The effect of temperature on the corrosion rate of Al-Si alloy in 1 M HCl solution has been also studied over the temperature range 25-55o C in the absence and presence of the investigated carbamidic thioanhydride derivatives, and also has been studied over the temperature range 25-45o C in the absence and presence of the investigated cyanoacetamide derivatives using electrochemical frequency modulation measurements.
Arrhenius plots of the corrosion current density (log kcorr) against reciprocal of absolute temperature (1/T) were found to be linear and obeyed the following equation: log kcorr = log A- Ea*/ 2.302RT
from calculated parameters we found that; 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 alloy surface. Thermodynamic functions of activation (ΔH* and ΔS*) were also calculated and discussed.
The results showed that the adsorption of these compounds obeyed Langmuir adsorption isotherm. The results were treated to obtain the free energy of adsorption ΔG°ads and the binding constant Kads using the kinetic model and Langmuir isotherm.
In conclusion: The potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation and gasometric measurements support the assumption that corrosion inhibition.