Fluorine-free, corrosion-resistant aluminum surfaces with nickel hydroxide and stearic acid superhydrophobic coatings.

This work presented a novel method for fabricating corrosion-resistant and fluorine-free superhydrophobic Al2O3/nickel hydroxide (NiOxHy)/stearic acid (STA) composite coating on the Al alloys. The Al2O3/NiOxHy composite film with an ideal micro-nanostructure was assembled on Al alloys by a one-step anodizing method. This facile and low-cost technique for fabricating superhydrophobic coating includes high-temperature anodizing in oxalic acid aqueous solution with Ni2+ and subsequent spin coating of the STA layer. The superhydrophobicity of as-fabricated film results from the hierarchical micro-nanostructure of Al2O3/NiOxHy and the coverage of STA with low surface energy, while the micro-nanostructure is beneficial to providing the appropriate roughness and maintaining more STA in its interstices and surface. The Al alloys with an optimal superhydrophobic coating displayed a static water contact angle of 164°, excellent self-cleaning ability, and superb corrosion-resistant efficiency of 99.6%. This facile method offers an effective strategy to fabricate corrosion-resistant protective coating on metallic substrates, which can significantly prolong the working lifetime of metallic materials in harsh environments. [ABSTRACT FROM AUTHOR]