Corrosion resistance of water repellent aluminum surfaces with various wetting morphologies

We investigated the improved corrosion resistance of micro/nanostructured aluminum surfaces by varying wetting morphologies. By combining the wet-chemical oxidation schemes and low surface energy coating, we induced three different wetting morphologies including superhydrophilic, Cassie-mode superhydrophobic and Wenzel-mode hydrophobic on micro/nanostructured aluminum surfaces. The superhydrophilic oxide layers provided approximately 30-76% improvement in the corrosion resistance compared to untreated ones. When a hydrophobic coating was added to the oxide layers and Cassie-mode superhydrophobicity was induced, all types of samples showed over 95% increase in the corrosion resistance compared with untreated ones. When the air trapped on the superhydrophobic surfaces was removed in a vacuum environment, the corrosion resistance decreased but still provided 70-98% increase compared with untreated ones. The present work showed that the superhydrophobic treatment is a very effective way to improve the corrosion resistance but the proper choice of the passivation layer and hydrophobic coating can provide a meaningful increase in the corrosion resistance. The present work further clarified the high corrosion resistance of superhydrophobic aluminum surfaces and will help to develop practical anti-corrosion resistance surfaces.