A pine needle-like superhydrophobic Zn/ZnO coating with excellent mechanochemical robustness and corrosion resistance

A novel pine needle-like superhydrophobic Zn/ZnO coating composed of micro-scale polyhedral Zn and radially aligned ZnO nanorods was fabricated on carbon steel substrate via the combination of two-step electrodeposition and chemical modification. The hierarchical structured Zn/ZnO-3 coating not only exhibited suprior super-repellency to different droplets such as cola, tea, soda water, milk, methylene blue and methyl orange, but also possessed excellent mechanochemical robustness and long-term corrosion resistance. [Display omitted] The superhydrophobic Zn-based coating with hierarchical structure has good prospects in metal anticorrosion. However, the practical application of superhydrophobic coating is still limited by the poor mechanical stability of micro/nano hierarchical structure. Herein, a robust superhydrophobic Zn/ZnO coating with pine needle-like structure and superior corrosion resistance was design and constructed. The micro-scale polyhedral Zn was fabricated on steel followed by the deposition of radially aligned ZnO nanorods, forming a novel pine needle-like hierarchical structure, which was finally modified by stearic acid. Notably, the pine needle-like structured Zn/ZnO (Zn/ZnO-3) coating exhibits excellent superhydrophobicity with contact angle of 166.8 ± 1.4° and sliding angle of 2.6 ± 0.5°. What's more, Zn/ZnO-3 coating maintains superhydrophobicity after suffering from strong acid/alkali, tape peeling, water drop impact and sandpaper abrasion tests. Compared with carbon steel and hydrophobic Zn coating, the corrosion current density of superhydrophobic Zn/ZnO-3 coating is decreased by approximately 4 and 3 orders of magnitude, respectively. The superior mechanochemical stability and anti-corrosion performance of superhydrophobic Zn/ZnO-3 coating is ascribed to its pine needle-like structure. Overall, this work provides a novel strategy to design hierarchical structured superhydrophobic surfaces with excellent mechanochemical stability and corrosion resistance, holding great prospects in metallic corrosion protection.