Superhydrophobic surfaces are attractive because of their special wettability properties. In recent years, artificial superhydrophobic surfaces have been studied extensively because of the demand for self-cleaning materials.1-6 The contact angle of water on a clean surface is a measure of its hydrophobicity. A water contact angle larger than 150° and a sliding angle less than 10° are the key characteristics of superhydrophobic surfaces. The wettability of a surface is controlled by its surface structure and chemical properties. In nature, many species demonstrate superhydrophobicity (e.g., lotus leaves and spiders).7-11 The self-cleaning properties of lotus leaves are based on its papillae structure and wax coating. Coating a solid with a low surface energy material increases the water contact angle however; the contact angle of a flat surface generally does not exceed 120°. Therefore, it is necessary to alter the surface roughness to realize the high contact angle required for superhydrophobicity. A nano-to-micro-scale rough surface has been proven to be important for generating superhydrophobicity and the self-cleaning effect. Nano/micrometer binary structures create a rough surface that contains a large amount of air, which repels a water droplet. In general, the water contact angle is directly proportional to the amount of air trapped between the rough surface and water. To imitate the lotus leaf structure, many methods have been reported that alter a surface's roughness and structure, such as lithographic patterning, and aluminum 27,28 have been achieved. Magnesium is a key metal in the current industry because it has certain predominant physical properties, such as its light weight. Owing to its physical and mechanical properties, magnesium and its alloys are used in many industrial applications, such as airplanes, automobiles, ships, and cellular phones.However, in practical applications, magnesium has a critical limitation, that is, low corrosion resistance. The fabrication of a superhydrophobic surface on magnesium would be a promising method to improve surface performance. The superhydrophobic surface on magnesium would reduce the full contact of the surface with water, which is one of the important factors required to overcome extremely low corrosion resistance.Since the fabrication of a superhydrophobic surface on a magnesium alloy was first published in 2007, 29 a few methods have been reported on the superhydrophobic treatment of magnesium alloy surface. 22,23,30 Various methods have been proposed to achieve this, such as chemical and plasma etching, electrochemical deposition, and the sol-gel method.In this paper, we describe a simple and efficient process for the fabrication of a superhydrophobic surface on magnesium alloy. This process combines chemical etching and treatment with stearic acid.
Experimental SectionMagnesium flakes (AZ31) with a size of 0.5 cm × 0.5 cm × 0.01 cm were cleaned ultrasonically in a solution of ethanol and distilled water for 5 min. The pieces were then immersed in a 5...
