| Aluminum and its alloys have the characters such as good conductivity, thermal conductivity, ductility, and good mechanical processing property. Consequently, they are the largest used and applied non-ferrous metals. In addition, aluminum alloy possesses the advantages as good appearance and low mass, and it also has better corrosion resistance than steel and other metals to some extent. Therfore, it has been widely used in people’s daily life and industrial fields. However, aluminum alloy can be easily corroded in acid, alkali, and some wet or salty environment, and icing or frosting phenomenon can take palce at the aluminum alloy surfaces in extreme climates. Additionally, the surface of aluminum alloy can be easily polluted under the atmospheric environment or some special conditions. All of these can hinder the practical application of aluminum and its alloy in various degrees. Due to superhydrophobicity has the ability to inhibit the corrosion of materials and to delay the freezing or frosting time, and it also has strong self-cleaning or anti-adhesion property. Thus, it is a very effective option to introduce the superhydrophobic film on aluminum and its alloy surfaces in order to improve the properties of anti-corrosion, anti-icing, anti-frosting, and self-cleaning.In this dissertation, the superhydrophobic aluminum alloy surfaces are developed successfully through a facile and feasible two-step method（namely, boiling water treatment + DMF-STA-H2 O immersion） or one-step method（i.e., DMF-STA-H2 O immersion）. The microstructure, chemical structure, corrosion resistance, anti-icing, anti-frosting, and self-cleaning performance of the as-prepared superhydrophobic surfaces are studied thoroughly, and the main contents and results are as follows:（1） Fabrication of the superhydrophobic aluminum alloy surface with two-step method: The superhydrophobic aluminum alloy surface with a contact angle of 156.6° and a sliding angle of less than 3° is fabricated successfully by a low-cost and environment-friendly two-step method. The effects of boiling water treatment time, DMF-H2 O volume ratio, and STA modification time on the surface microstructure and wettability of the superhydrophobic aluminum alloy surfaces are investigated, and the optimum technological conditions are finally determined as follows: boiling water treatment time for 5 min, DMF-H2 O ratio of 1:1, and STA modification time for 24 h. Results show that the aluminum alloy is endowed with the superhydrophobicity grounded on the synergistic effect of homogeneous layer structure composed of large numbers of micro- and nano- pore petals and low surface energy material.（2） Preparation of the superhydrophobic aluminum alloy surface with one-step method: The superhydrophobicity of aluminum alloy surface is successfully endowed by one-step method, and the effects of DMF-H2 O volume ratio, and STA modification time on the surface microstructure and wettability of the superhydrophobic aluminum alloy surfaces are explored. Results show that the superhydrophobic film with a water contact angle of 155.5° and sliding angle less than 3° can be achieved when the volume ratio of DMF-H2 O, and the STA modification time is 1:3, and 35 h, respectively. Because of the large numbers of micro- and nano- hole structure forms on aluminum alloy surface, while the long alkyl chains with low surface free energy graft on its surface. Consequently, great amounts of air are captured in the hole, and water droplets cannot penetrate into it and can only contact with the surface protuberances. Furthermore, even the slight disturbance can lead to the water droplets roll off the surface. So the aluminum alloy surface obtains the excellent superhydrophobicity.（3） Corrosion resistance of the superhydrophobic aluminum alloy: The corrosion resistance of the superhydrophobic aluminum alloy is investigated by the electrochemical test and salt water immersion. Electrochemical measurements show that the corrosion potential of the superhydrophobic aluminum alloy surfaces positively increases and the corrosion current density significantly decreases as compared to that of the blank ones. The surface wettability, surface morphology, and chemical structure of both blank and superhydrophobic aluminum alloy samples after immersed in salt water for 0-90 days are analyzed, and results demonstrate that pitting is the main cause of corrosion, and the main corrosion product is Al（OH）3. The corrosion products generated on the superhydrophobic surfaces are far less than that on the blank ones. All of these results indicate that surface superhydrophobicity can significantly improve the corrosion resistance of aluminum alloys, and which is due to the superhydrophobic coating can effectively capture large amounts of air at the interfaces and prevent the corrosive Cl- dissolved in water from directly contacting with aluminum alloy surface. Thus the anti-corrosion property of aluminum alloy is improved.（4） Anti-icing and anti-frosting performance of the superhydrophobic aluminum alloy surface: By simulating the frozen and wet weather, the anti-icing and anti-frosting performance of the as-prepared superhydrophobic sample is investigated. Results show that the superhydrophobic aluminum alloy surface can postpone the freezing time for 5-9 min as compared to the blank sample surface at the same temperature. Under the same freezing time, the freezing temperature for water droplets on superhydrophobic surfaces can reduce ca. 2 oC than on the blank sample surface. In addition, the superhydrophobic surface can significantly hinder the growth of frost crystals, and the melting frost crystals can transform into easily rolling droplets. Finally, the mechanism of anti-icing and anti-frosting of the superhydrophobic surface is deduced and discussed.（5） Self-cleaning behavior of the superhydrophobic aluminum alloy surface: The self-cleaning performance is examined with following methods. a) Using the carbon powder, chalk dust, and cigarette ash as the simulating pollutants, the ability of water droplets rolling and taking away pollutants on the blank and superhydrophobic aluminum alloy surfaces is examined. b) By contrasting the salt dust adsorption on the blank and superhydrophobic aluminum alloy surface after immersed in salt water for some period. Results show that as compared to the blank sample, rolling water droplets can take away pollutants at the superhydrophobic surfaces completely, and the superhydrophobic surface possesses the ability of preventing the adsorption of salt dust just grounded on its strong hydrophobicity and low adhesive force. This suggests that the superhydrophobic aluminum alloy surface has excellent self-cleaning performance.（6） Optimization of superhydrophobic surface fabrication method: Aiming at the cumbersome steps of polishing and removing the surface oxide layer on aluminum alloy surface, it has been found that the superhydrophobic surface can be successfully fabricated without polishing and grinding, which can simplify the superhydrophobicity process of aluminum alloy. |
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