| Superhydrophobic surface, with water contact angle greater than 150 degree and sliding angle less than 10 degree, has attracted a great deal of attention due to its greatly potential applications in self-cleaning, anti-icing, anti-fouling, anti-corrosion and oil-water separating. In this paper, superhydrophobic surfaces have been fabricated on Q235 steel by chemical deposition, salt immersion and Ultra Ever Dry as a commercial superhydrophobic coating respectively, and then the formation mechanism and the durability of these superhydrophobic surfaces were studied. The results are listed:1. Chemical deposition and salt immersion were ultilized to render Q235 steel superhydrophobic. The results of the characterization indicated that the immersion of steel in 0.1M CuCl2 solution for 1 min had given rise to the growth of the nano/micro-structure with numerous branch crystals on the steel surface. After modification, superhydrophobic surface could be generated on steel with the CA and SA of 156° and 2° respectively; The sealed immersion process of steel in 3.5 wt% NaCl solution at 90℃ for 24 h had accelerated the chemical etching of the steel surafce, which could induce the formation of the petal-like nano/micro-structure. Under fluorinated treatment, the obtained surface acquired the property of superhydrophobicity with the CA and SA of 155° and 1° respectively. The study showed that both the mechanical and chemical durability of these two superhydrophobic surfaces were unsatisfied.2. Superhydrophobic surface of Q235 steel with the CA and SA of 155° and 2° was obtained by the spray of Ultra Ever Dry as a commercial superhydrophobic coating. Under the characterization of SEM, XRD and FTIR, we figured out that this superhydrophobic coating mainly consisted of the chlorinated-rubber base bottom coating with the formation of micro-structure and the top coating whose main composition is fluorinated SiO2 which could pile to the nano-structure with numerous nano-pores.3. The study of sandpaper abrasion test showed that the abrasion process had destroyed both micro/nano-structures after 12 cycles of abrasion test. The water-jet impact had caused the loss of nanoparticles of coat, which could lead to the loss of superhydrophobicity after 90 min under 100 kPa pressure.4. The effect of solution with different pH on superhydrophobic coating sprayed on steel showed this coating could maintain its original superhydrophobicity in the solution with pH value from 1 to 11, however, the immersion of the extremely alkaline solution (pH=14) could lead to the loss of superhydrophobicity of this coating, which should be attributed to the fact that the harsh alkali solution (pH=14) had "eated" the fluorinated SiO2 nanoparticles which is the key to the superhydrophobicity, and then the original nano-structure of surface had been destroyed and the surface energy had increased greatly.5. Under the salt solution, this commercial coating exhibited high chemical durability and could improve the anti-corrosion of steel in similar seawater, the mechanism of anti-resistance is that the abundant air trapped in hierarchical rough structures could effectively prevent the infiltration of corrosive ions. The superhydrophobic coating, however, is unable to improve the anti-corrosion of steel in the condition of salt spray since the superhydrophobic coating with porous structures will allow etching molecules to pass through the porous and induces the corrosion of the metal substrate.
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