Superhydrophobic and Self-Cleaning Aluminum via a Rapid and Controlled Process

Abstract

Superhydrophobic and self-cleaning materials have been an extensive topic of research owing to their corrosion resistance, antifouling, and anti-icing properties. In the past, superhydrophobicity in aluminum has been obtained by a variety of techniques involving etching by sandblasting, chemical etching, boiling in water, etc. followed by treatment with a fluorochemical and organic solution. However, these techniques are not controlled, might not be easy to implement on a large scale, and mostly make use of fluorochemicals, which are risky for human health and the environment. Therefore, there is a need for a rapid and controlled fabrication process that can provide patterned superhydrophobicity without compromising the environment or the human health. Here, a rapid, controlled, and environmentally friendly procedure for fabricating a superhydrophobic and self-cleaning aluminum surface has been developed, achieving a contact angle of 158.06° and a sliding angle of 1.94°. In the two-step process, a rough surface was obtained using the laser etching technique in under 3 min, which resulted in a precisely controlled pattern with a dual-scale roughness on the surface (∼20–30 μm). Finally, a low surface energy was imparted to the surface by treatment with stearic acid where a low concentration of 2 × 10–4 M and no more than 10 s of exposure was found to be sufficient. Unlike various superficially coated materials, this superhydrophobic surface is durable and does not lose its properties after dipping in water for up to 4 days, encountering fine sand or mud, or at extreme surrounding temperatures of −18 to 100 °C. Thus, this rapid and controlled process for obtaining superhydrophobic aluminum potentially can be deployed for large-scale, structural applications.