Fabrication and theoretical explanation of the superhydrophobic CuZn coating with dandelion-like CuO microstructure

In this work, a CuZn coating with dandelion-like CuO microstructure was fabricated on pipeline steel surface by a simple two-step combined method of electrodeposition and chemical oxidation. This coating was then coated with a thin pentadecafluorooctanoic acid to achieve superhydrophobic, with the contact angle of water about 156.81° and the sliding angle around 3°. When a water droplet contacted on the CuZn coating surface, the dandelion-like CuO microstructure was seen as the dual-scale structure that was proposed to be composed of spherical and pillared microstructures. Based on the Wenzel's and Cassie's formulas, the theoretical explanation was used to confirm the Cassie-Cassie wetted state between water droplet and the dandelion-like hierarchical superhydrophobic coating according to the geometric parameters of the surface morphology. Meanwhile, the superhydrophobic CuZn coating had the ability to repel the impinging water droplets and excellent long-term, thermal, solution immersion and chemical stability. Such robust superhydrophobic CuZn coating with hierarchical microstructures was expected to have various potential applications in our daily life.