Protective superhydrophobic coatings on the surface of anodized aluminum

• A.A. Abrashov, A.I. Khafizova, N.S. Grigoryan, A.A. Petrushina, N.A. Asnis and T.A. Chudnova

D. Mendeleev University of Chemical Technology of Russia, Miusskaya sq. 9, 125047 Moscow, Russian Federation

Abstract: One of the ways to protect metal surfaces from a corrosive environment that recently gained popularity is the creation of continuous surface films that feature water-repellent properties and the self-cleaning ability (the so-called superhydrophobic films). In academic and engineering publications, the term “superhydrophobic surfaces” is used for surfaces on which the contact angle of wetting with water and aqueous solutions exceeds 150°, a drop of water rolls off the surface when it is tilted by no more than 10°, and the surface exhibits a pronounced self-cleaning tendency. A known drawback of chemically produced superhydrophobic coatings (SHCs) is their low wear resistance. In this study, we examined the possibility of enhancing the wear resistance of SHC by preliminary anodic oxidation of aluminum and its alloys. An electrolyte for anodic oxidation of the surface of an AMg6 aluminum alloy containing 15 wt.% H₂SO₄ and 15 wt.% H₃PO₄ was developed. It was found that anodizing in the electrolyte based on sulfuric and phosphoric acids results in the formation of anodic oxide films with the required well-developed microstructured relief. It has been found that the preliminary anodizing of the aluminum surface leads to an increase in the adhesion strength with the next SHC and, consequently, to an increase in its wear resistance. Corrosion tests in a salt fog chamber showed that the developed coating withstands 830 hours in salt fog (5% NaCl) before the first centers of corrosion of the substrate appear, while the untreated aluminum alloy begins to corrode after 22 hours of exposure.

Keywords: corrosion protection, surface treatment, superhydrophobic coatings, stearic acid, aluminum anodizing, hydrophobization, contact angle

Int. J. Corros. Scale Inhib., 2023, 12, no. 3, 1013-1027
doi: 10.17675/2305-6894-2023-12-3-13

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