Fabrication of mechanically robust superhydrophobic aluminum surface by acid etching and stearic acid modification

The aluminium surface with multi-scale structure has been fabricated via a facile and rapid solution-phase etching method by HCl/H₂O₂ etchants. After modification with stearic acid solution, the wettability of the etched aluminum surface turns into superhydrophobicity with an optimal water contact angle of 160° ± 2° and a sliding angle of 4° ± 1°. The processing conditions, such as the etching time, modifier types and the concentration of H₂O₂ are investigated to determine their effects on the surface morphology and wettability. As a result, the obtained sample shows excellent anti-adhesion property and bouncing phenomenon of water droplet. It can withstand mechanical abrasion for at least 100 cm under 12.3 kPa, or hydrostatic pressure under 24 ± 1 kPa without losing its superhydrophobicity, suggesting superior mechanical durability. Moreover, the surface also remains superhydrophobicity even after contacting corrosive liquids or long-term exposure in air over 100 days. Such a mechanically durable superhydrophobic aluminum surface can provide a promising practical application in various fields.