Fabricating Superhydrophobic Protective Films with Enhanced Self-Cleaning and Anti-Corrosion Properties through Multiple Anodic Oxidations on Aluminum Alloys

The development of aluminum (Al) alloys with superb anti-corrosion and self-cleaning properties for prolonging the working life and reducing maintenance cost is a hot topic of concern. Since anodic oxidation has been proven to be an effective technique to prepare micro or nanostructures on Al alloys surface, this study proposes a novel and scalable multiple anodic oxidations method with gradient current densities for fabricating hierarchical micro-nanostructure film with appropriate roughness on Al alloys, while the SiO2-silane film reduced the surface free energy and enhanced the surface chemical inert state. As expected, the surface of Al alloys modified with the multiple anodic oxidations and SiO2-silane film has the most substantial hydrophobic properties, with contact angle up to 166 degrees, rolling angle as low as 3.17 degrees and excellent non-sticking effect of water droplets. This method enables the Al alloys surface to have excellent self-cleaning performance and corrosion resistance with protection efficiency up to 98.81 %. This multiple anodic oxidations method has a wide range of references for the modulation of micro-nanostructure on Al alloys surface and other metallic substrates to assemble superhydrophobic protective films.