Electrochemical Corrosion of Bulk Nanocrystalline Aluminum in Acidic Sodium Sulfate Solutions at Room Temperature

The corrosion properties of metallic materials are usually associated with the compactness of the oxide film and electrochemical parameters, such as corrosion potential, corrosion current density, pitting potential, etc. The valence electron configurations of metallic materials can also affect their corrosion properties because the nature of their corrosion processes involves the exchange and transportation of valence electrons between metallic atoms and ions. In the present work, the electrochemical corrosion of bulk nanocrystalline aluminum (BN-Al) produced by severe rolling technique and its conventional polycrystalline aluminum (CP-Al) counterpart in 0.01, 0.05, and 0.1 M HCl + 0.25 M Na 2 SO 4 solutions at room temperature was studied by potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy. The uniform and pitting corrosion resistances of BN-Al were simultaneously enhanced in comparison with those of CP-Al. The ion adsorption in oxide films along depth profiles on BN-Al and CP-Al and their valence electron configurations were characterized by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy, respectively. The enhanced corrosion resistance of BN-Al resulted from its valence electron configuration rather than the Cl –, SO 4 2–, and Na + adsorptions and the oxide film on BN-Al.