الفهرس 
1.2 Electrochemical characteristics of magnesium alloysOnly 14 pages are availabe for public view
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Abstract
In this work the electrochemical behavior of pure Mg, Mg-Al-Zn and Mg-Al-Zn-Mn alloys was investigated in aqueous acidic, neutral and basic solutions. Conventional electrochemical techniques such as open-circuit potential measurements, polarization methods and electrochemical impedance spectroscopy (EIS) were used. The results have shown that the rate of corrosion in acidic solution is relatively high compared to that in neutral or basic solutions. The presence of Al, Zn and Mn as alloying elements decreases the rate of corrosion of the alloy. The activation energy of the corrosion process occurring at the surface of Mg or Mg-alloys in aqueous solutions is less than 40 kJ mol-1 indicating a diffusion controlled one electron transfer electrode process. The impedance data were fitted to an equivalent circuit model that explains that different electrochemical processes occurring at the electrode/electrolyte interface. Also, the inhibition of corrosion of the two Mg alloys in neutral solutions by using different amino acids as environmentally safe corrosion inhibitors was investigated. Generally, the corrosion inhibition efficiency in presence of cystein was found to be higher compared to the other amino acids. The calculated inhibition efficiencies were in the range between 32 to 92%. The presence of aromatic ring and hetero atoms such as sulfur and nitrogen in the structure of the inhibitor leads to a significant increase in the corrosion inhibition efficiency. The mechanism of the corrosion inhibition process is based on the adsorption of the amino acid molecules on the active corrosion sites and/or the deposition of corrosion products on the metallic surface and the formation of a protective layer. The calculated free energy of adsorption of phenyl alanine on Mg-Al-Zn and Mg-Al-Zn-Mn alloys reveals a physical adsorption of the inhibitor on the alloy surface.