Controlled fabrication of NiO/ZnO superhydrophobic surface on zinc substrate with corrosion and abrasion resistance

The paper reports on the preparation of NiO/ZnO superhydrophobic surfaces (SHS) on zinc via chemical substitution/deposition and thermal annealing. The resulting surfaces display superhydrophobic behavior with a water contact angle (WCA) of 153 degrees and a sliding angle (SA) of similar to 5 degrees without the use of any additional organic coating. Using the Cassie-Baxter equation, it is found that about 91.6% serves as the contact area of the water droplet and air, leading to the roll down property of the water droplet on the surface. The surface superhydrophobicity is controlled and influenced by various preparation conditions: the thermal treatment, which causes the generation of NiO and ZnO layers, and the formation of polygonal honeycomb structures and disappearance of silk flower-like clusters. The resulting NiO/ZnO SHS exhibit roll down, anti-corrosion and anti-abrasion properties. The corrosion current density of the NiO/ZnO SHS (5.7 x 10(-4) A cm(-2)) is decreased by more than 1 order of magnitude when compared to the untreated Zn surface (1.4 x 10(-3) A cm(-2)). EIS results also indicate that the SHS possesses higher anti-corrosion performance. The superhydrophobic sample, after annealing treatment, can sustain a collapsing force of about 7.8 N, which is better than the superhydrophilic sample without annealing treatment (similar to 5.2 N). This controlled fabrication process may offer new avenues for designing superhydrophobic surfaces with corrosion resistance for more practical applications. (C) 2017 Elsevier B.V. All rights reserved.