Characterization of water-repellent and corrosion-resistant superhydrophobic surfaces on galvanized steel
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Characterization of water-repellent and corrosion-resistant superhydrophobic surfaces on galvanized steel Thet Htet Naing, Vishnu Rachpech, Somjai Janudom, Narissara Mahathaninwong
© American Coatings Association 2020 Abstract Corrosion-resistant superhydrophobic surfaces were successfully fabricated on galvanized steel through a wet oxidation treatment and stearic acid modification. In this work, the formation mechanism of superhydrophobic surfaces and structures were characterized with contact angle meter, scanning electron microscope (SEM), X-ray diffractometer (XRD), and Fourier transform infrared spectroscopy (FTIR). The surface properties of superhydrophobic and non-superhydrophobic surfaces were assessed by calculating surface free energy (γ) and work of adhesion (Wst). Moreover, the corrosion behavior and durability of superhydrophobic surfaces were examined in 3.5 wt% NaCl solution for up to 14 days. Superhydrophobic galvanized surfaces with WCAs of 168° (γ=0.01 mN/m and 1.57 mN/m) and 162° (γ=0.04 mN/m and Wst = 3.52 mN/m) were successfully obtained by modifying HCl etched surfaces with ethanolic stearic acid, with or T. H. Naing, V. Rachpech (&), S. Janudom, Department of Mining and Materials Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand e-mail: [email protected] T. H. Naing e-mail: [email protected] S. Janudom e-mail: [email protected] T. H. Naing, V. Rachpech, S. Janudom, N. Mahathaninwong, Center of Excellence in Metal and Materials Engineering (CEMME), Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand e-mail: [email protected] N. Mahathaninwong, Faculty of Sciences and Industrial Technology, Prince of Songkla University, Surat Thani Campus, Muang, Surat Thani 84000, Thailand
without wet oxidation. According to the results, a zinc stearate layer on the surfaces effectively enhanced their corrosion resistance by numerous air pockets on the surfaces with hierarchical micro-/nanostructures that inhibited penetration by the NaCl solution. Moreover, superhydrophobic as-synthesized ZnO surface by wet oxidation had better corrosion durability than a superhydrophobic etched surface because of the strong physical and chemical bonding of stearic acid onto the as-synthesized ZnO nanorods. Keywords Corrosion resistance, Galvanized steel, Superhydrophobic surfaces, Wet oxidation, ZnO nanorods, Zinc stearate layer
Introduction It is well known that galvanized zinc coatings are extensively used as a sacrificial anode to protect steel structures against corrosion in the surface finishing industry around the world.1 However, an additional surface treatment is usually required to improve the anticorrosion performance of zinc coatings because of the high electrochemical reactivity of zinc.2 In recent years, many studies have addressed the artificial fabrication of superhydrophobic surfaces with nonwetting properties to serve as effective barriers inhibiting corrosion of zinc.3,4 Artificial superhydrophobic surfaces with a minimu
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