A cost-effective method to create physically and thermally stable and storable super-hydrophobic aluminum alloy surfaces

• Facile fabrication of desirable roughness on aluminum alloy surface by base treatment and acid solution etching
• Surface modification of roughened aluminum alloy by relatively inexpensive chlorosilanes
• The chlorosilane modified Al alloy showed WCA of 165 ° and CAH of less than 3 ° and proper thermal stability up to 375 °C
• The surfaces’ hydrophobicity were maintained after 100 hours of immersing in water and storing for 180 days

Physical stability and thermal stability of super-hydrophobic surfaces are some of the most significant issues for applying them in industry. A facile and cost-effective method has been developed to create thermally and physically stable and storable super-hydrophobic aluminum alloy surfaces. Chemical etching by sodium hydroxide and a solution of acetic acid and hydrochloric acid were used to create micro-nano structures over the surface and subsequently trichloro(octadecyl)silane (TCODS), trichlorododecylsilane (TCDS), and trichloro(octyl)silane (TCOS) were used to modify these roughened surfaces. The effects of different etching processes, different type of chlorosilanes, and the amount of modifiers on the resultant aluminum alloy surfaces hydrophobicity were also investigated. The resulting surface morphologies, compositions, roughness, and water contact angle were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), 3D surface profilometer, and water contact angle (WCA) meter, respectively. Photron APX-RS high speed camera was used for imaging contact angle hysteresis (CAH) and dynamic droplet/surface interaction. The WCA and water contact angle hysteresis (CAH) of the aluminum alloy surfaces modified by TCODS reached to 165° and less than 3°, respectively; and it remained super-hydrophobic after 100 h immersing in water, 30 min ultra-sonication, stored for more than 30 days under ambient condition, and heated to 375 °C for 20 min.

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