Corrosion Resistance Improvement of Aluminum by Hydrophobic Anodic Oxide Film

Diminishing surface wettability is an effective method to improve corrosion resistance of aluminum. Various techniques for preparing hydrophobic surface have been reported, most of which use organic coating as the final step. The key point to diminish surface wettability is to form a fine regular surface structure, and the porous type anodic oxide film (PAOF) has nano-pore structure, therefore promising for being utilized to develop hydrophobic surface combined with other treatment. In this study, a hydrophobic surface was prepared on aluminum sheet by constant-current anodic oxidation, followed by desiccation treatment. The surface morphology was investigated by SEM, and chemical composition was analyzed by AES and XPS measurement. The result showed that topside morphology of porous layer was greatly influenced by both desiccation time and temperature, without an evident change in chemical composition. Corrosion behavior of samples was investigated in 0.6 kmolm NaCl solution in various immersion time. A decreasing quantum of corrosion products on anodized surface and hydrophobic surface indicated an improvement of corrosion resistance. Potentiodynamic polarization measurement was employed to confirm the corrosion resistance improvement of hydrophobic treatment in the same solution, and the result showed current density of anodized sample decreased more after desiccation process.