Research on the Fabrication of Superhydrophobic Surface on Typical Metal Substrate

Superhydrophobic surface is a kind of valuable bionic materials with many special properties, such as self-cleaning, anti-icing/frosting, drag reduction and corrosion resistance, which is widely applied in the automobile, livelihood, military and the other fields. Recent there are many fabrication methods to obtain the superhydrophobic surface on many materials, especially on metal surface, but all the fabrication methods for the metal substrates have problems of complicated process techniques, high cost, environment pollution and some others, that strongly limited the application of the superhydrophobic surface. To improve those deficiencies, three studies were carried out for the fabrication of superhydrophobic surface on magnesium alloy, carbon steel, and pure aluminum substrates.The electrochemical method was adopted to construct the coarse structures on magnesium alloy substrate by the neutral NaClO3electrolyte and NaBr electrolyte, and then modified with the FAS, to obtain the superhydrophobic surface on magnesium alloy. The study on fabrication parameters showed that the optimal current densities in the two electrolytes were both250mA/cm2, and the processing times were5min and7min in NaClO3electrolyte and NaBr electrolyte respectively. And under the optimal processing parameters, the corresponding contact angles reached167.4°and170.3°, titling angle were both1.5°. This fabrication method is very useful in fabricating magnesium alloy for little the environment pollution and low cost.A method combined chemical deposition with surface corrosion technique was proposed to fabricate superhydrophobic surface on carbon steel substrate. The method used CUSO4solution to deposit copper film on the substrate surface and etch the deposited surface by the mixed solution of NaOH and (NH4)2S2O8, then modified with the stearic acid to obtain the superhydrophobic surface. The study on the processing parameters showed that the optimal corrosion time was in the range of45-60min when the whole surface was well-distributed nanometer-needles consisted thicket structures. The corresponding contact angle reached165.9°, and good titling angle near0°。The measurements of surface components showed that the main chemical components was Cu(OH)2, and the stearic acid was covered on the surface. This method has the advantages in short processing time and low cost, that largely improved the efficiency in fabrication of carbon steel superhydrophobic surface.A one-step chemical method was suggested to fabricate superhydrophobic surface on metal surface and be used in fabricating pure aluminum. The aluminum substrate was etched by hydrochloric acid aqueous solution mixed with fluoroalkylsilane, to obtain the micro-structure and low surface energy modification in one step. The superhydrophobic surface by one-step method has little difference in superhydrophobicity with the surface by two-step method, the contact angel was163.01°, and titling angle was only1°。Detailed experiments showed that the concentration of fluoroalkylsilane had little influence to surface superhydrophobicity. This method has no modification time, which greatly improved the process efficiency.