A Comparative Study on the Electrochemical Corrosion Behavior of Microcrystalline and Nanocrystalline Aluminum in Natural Seawater

In this study, we compared the electrochemical corrosion behavior of a newly fabricated nanocrystalline pure aluminum to another microcrystalline aluminum using various electrochemical techniques in natural Arabian Gulf seawater. The nanocrystalline Al was fabricated using mechanical alloying technique. Cyclic potentiodynamic polarization showed that microcrystalline has lower corrosion current and corrosion rate with higher polarization resistance compared to the nanocrystalline Al. The change of current with time at -550 mV vs. Ag/AgCl revealed that the nanocrystalline Al had higher absolute currents. The scanning electron microscopy images showed that nanocrystalline Al surface was more corroding under the aggressiveness action of the seawater and the applied anodic potential value. This was also confirmed by the electrochemical impedance spectroscopy data, which indicated that the nanocrystalline Al shows lower polarization and solution resistances when compared to the microcrystalline Al. All results were in good agreement showing clearly that the nanocrystalline Al has less corrosion resistance and high corrosion rate in the Arabian Gulf seawater due to the presence of many active centers on its surface.