Preparation of super-hydrophobic aluminum by a novel immersion method using potassium permanganate solutions

A simple method of acid etching and surface passivation was developed for fabricating the super-hydrophobic surface on polycrystalline aluminum alloy. After the chemical etched surface was fabricated with the stearic-acid, the aluminum alloy surface exhibits a super-hydrophobic property with water contact angle of 151 degrees and contact angle hysteresis of 8 degrees. The surface morphology was inspected with scanning electron microscope, and it was found that the surface is configured in a labyrinthic porous structure with plateaus and caves of micro-nanostructure. The air cushion was formed in the caves between the surfaces. This micro-nano hierarchical structure plays an important role in the formation of the super-hydrophobicity. The super-hydrophobic phenomenon of the prepared surface was analyzed with Cassie theory, and the result shows that only about 16% of the water contact surface are contacted with the metal substrate and the rest 84% is contacted with the air cushion. The experimental results showed that aluminum of super-hydrophobic surface can be prepared by this simple method, the optimum process conditions found are after grinding, ethanol soaking, acetic acid soaking sixty hours, immersing in the 0.1mol/L potassium permanganate three hours after soaking and finally immersion in 1% stearic-acid for 30 minutes. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Chinese Materials Research Society