Fabrication of superhydrophobic Au-Zn alloy surface on a zinc substrate for roll-down, self-cleaning and anti-corrosion properties

Superhydrophobic Au-Zn alloy surfaces have been fabricated successfully on a zinc substrate via chemical substitution deposition and subsequent annealing treatment. The resulting surfaces exhibited remarkable superhydrophobicity with a WCA of 170 +/-2 degrees and a WSA smaller than 1 degrees without any organic modification. The surface morphologies and chemical compositions were investigated using field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the surface roughness was analyzed by atomic force microscopy (AFM). The theoretical mechanism for superhydrophobicity and wettability were also analyzed. The surface wettability changed from superhydrophilicity to superhydrophobicity with a stable Cassie-Baxter state via thermal treatment, which caused the generation of Au-Zn alloys (including AuZn3 and AuZn) and ZnO, and the formation of micro-/nano-binary architectures. The resulting superhydrophobic Au-Zn alloy surfaces exhibited exquisite roll-down, self-cleaning, and excellent anti-corrosion properties, and also had a firm mechanical property about 10 N, and this might have important values for more potential applications. The corrosion current density was reduced by more than 2 orders of magnitude for the resulting superhydrophobic surface in comparison with the untreated zinc surface and this should be ascribed to the contribution of Au-Zn alloys on the surface.