Corrosion Behavior Of Nanocrystalline Pure Aluminum In Acidic Solutions

Aluminum and aluminum alloys are widely used in various fields of modern society due to their excellent properties, such as lightweight, good electric and thermal conducting performance. However, in many corrosion environments, the corrosion of aluminum and aluminum alloys happens frequently, which affects their lifetime for application and may cause accidents further. Therefore, the study of the corrosion properties of aluminum and aluminum alloys is of great significance for the development of new materials of aluminum and surface modification technology.In recent years, nanocrystalline materials have been received much attention in many fields for their unique properties. The investigation on corrosion behavior of nanocrystalline materials is becoming an important issue in the corrosion field. The microstructures of materials can determine their physical and chemical performances. Therefore, the corrosion resistance of the materials will be changed by nanocrystallization. In this work, we produced bulk nanocrystalline pure Al by severe rolling technique. The corrosion behaviors of the nanocrystalline materials as well as the conventional polycrystalline pure aluminum as a contrast experiment, were studied in different corrosion environment.One object of this work is focus on the pitting corrosion behavior of nanocrystalline pure aluminum (BN-Al) and conventional pure aluminum (CP-Al) in HCl solutions. Through the immersion test and combined with surface analysis techniques such as scanning electron microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS), we studied the natural corrosion behavior of BN-A1in HCl solution. The investigation results indicated that the corrosion resistance of pure aluminum was improved after nanocrystallization. This is attributed to the fact that the oxide film formed on BN-Al corrosion surface was more compact than that formed on its counterpart aluminum. Meanwhile, the surface activity of chloride ions in the oxidation film decreased significantly, that caused lower dissolution of the membrane and reduced the risk of occurrence of pitting corrosion. The other object of this work is focus on the corrosion properties of BN-Al in different acidic solutions. Electrochemical methods such as potentiodynamic polarization curves, impedance spectrum (EIS) and combined with SEM surface analysis technique were employed in this work. The results indicated that the corrosion resistances of BN-Al were enhanced in solutions containing SO42-and Cl-. This is due to the fact that the oxide film formed on the surface of BN-Al was more stable. Therefore, the corrosion resistance of pure aluminum had been improved after nanocrystallization.In addition, a preliminary investigation on the electrochemical corrosion behavior of BN-Al in organic formic acid solution was studied as well. And the experiment results showed that the corrosion resistance of BN-Al was larger than that of CP-Al in formic acid solutions at lower concentrations.