A labyrinth microstructure interconnected by micron and submicron acicular structures was successfully prepared by immersing nickel-aluminum bronze in 9 wt% FeCl3·6H2O solution at room temperature for 40 min. After being modified with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (FAS-17), the microstructure surface displays robustly low-adhesion superhydrophobicity, and the water contact angle is above 160 ° on it. In addition, the superhydrophobic surface exhibits excellent corrosion resistance and stability in 3.5wt % NaCl aqueous solution and corrosion solution with different pH values.
It is generally recognized that superhydrophobic surfaces in water may be used for corrosion resistance due to the entrapped air in the solid/liquid interface and could find potential applications in the protection of ship hull. For a superhydrophobic surface, as its immersion depth into water increases, the resultant hydrostatic pressure is also increased, and the entrapped air can be squeezed out much more easily. It is therefore predicted that high hydrostatic pressure would cause an unexpected decrease in corrosion resistance for the vessels in deep water (e.g., submarines) because of the unstable entrapped air. In this work, in order to clarify the role of hydrostatic pressure in the corrosion behavior of superhydrophobic surfaces, two typical superhydrophobic surfaces (SHSs) were prepared on bare and oxidized aluminum substrates, respectively, and then were immersed into the NaCl aqueous solutions with different depths of ∼0 cm (hydrostatic pressure ∼0 kPa), 10 cm (1 kPa), and 150 cm (15 kPa). It was found out for the SHSs on the oxidized Al, as the hydrostatic pressure increased, the corrosion behavior became severe. However, for the SHSs on the bare Al, their corrosion behavior was complex due to hydrostatic pressure. It was found that the corrosion resistance under 1 kPa was the highest. Further mechanism analysis revealed that this alleviated corrosion behavior under 1 kPa resulted from suppressing the oxygen diffusion through the liquid and reducing the subsequent corrosion rate as compared with 0 kPa, whereas the relatively low hydrostatic pressure (HP) could stabilize the entrapped air and hence enhance the corrosion resistance, compared with 15 kPa. The present study therefore provided a fundamental understanding for the applications of SHSs to prevent the corrosion, especially for various vessels in deep water.
In recent years, inspired by “biomimicry”, superhydrophobic surfaces have gained significant attention. Superhydrophobic surfaces demonstrate notable advantages in addressing interfacial issues, and superhydrophobic coatings exhibit excellent waterproofness, anti-fouling, self-cleaning, anti-corrosion, and additional capabilities, making them promising next-generation waterproof materials. However, the complex preparation process, coupled with poor wear resistance and environmental durability, severely limits their practical applications. Therefore, this article started from simplifying the preparation process and improving the durability of the coatings. Epoxy resin (E51) was used as the film-forming material, and carbon nanotubes (CNTs) and dual-sized SiC particles (nano-SiC and micro-SiC) were used as the fillers. Room temperature vulcanized silicone rubber (RTV) was used as a binder interacting with epoxy resin to promote the interface interaction between the fillers and the polymers. This process resulted in the successful preparation of superhydrophobic coatings with outstanding comprehensive performance. When the ratio of μ-SiC to n-SiC was 1:1, the prepared coating exhibited the best superhydrophobic properties with a water contact angle (WCA) of 167.4° and a sliding angle (SA) of 4.6°. Even after undergoing severe mechanical tests, such as sandpaper abrasion for 1000 cycles, sand impact for 100 cycles, cross-cut test, and tape-peeling for 70 cycles, the coatings still maintained their non-wetting Cassie-Baxter state. Furthermore, even after immersion in strong acid, strong alkali and 3.5 wt% NaCl solutions for 6 days, keeping at 500 ℃ for 2 hours, and exposure to ultraviolet for 6 days, the coatings still exhibited excellent superhydrophobicity. This suggested that the prepared coating had excellent chemical stability and high-temperature resistance. In addition, the superhydrophobic coating exhibited exceptional capabilities in self-cleaning, anti-corrosion, anti-icing, and de-icing properties. Furthermore, this coating, applicable to diverse substrates including board, steel, paper, and glass, demonstrated an impressive water contact angle (WCA) and sliding angle (SA). The spraying method offers the benefits of simplicity and cost-effectiveness. This is poised to significantly broaden its practical applications in various fields, including construction, transportation, and the chemical industry.
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