Superamphiphobic aluminum alloy surfaces with micro and nanoscale hierarchical roughness produced by a simple and environmentally friendly technique

In this study, superamphiphobic (SAP) metallic aluminum (Al) alloy 2024 surfaces were produced with water and oil contact angles (CAs) of more than 150° and sliding angles of less than 10°. The two simple and environmentally friendly techniques of mechanical sanding and boiling water treatment were used to introduce micro and nanoscale roughnesses, respectively, which resulted in a hierarchical morphology. Surface energy of the rough surfaces was reduced by coating them with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane agent. SAP property was absent for samples with micro or nanoroughness only, and it emerged only after both kinds of roughnesses were introduced. The highest CAs approaching 158° for water, 156° for ethylene glycol, and 154° for peanut oil were obtained after forming hierarchical structures involving shapes of microgrooves obtained by one-directional sanding and nanograss by immersing in boiling water for 1 min. The effects of the two approaches of random and one-directional sanding using various sandpaper grit sizes, and different time periods of treatment with boiling water on the wettability of surfaces were also investigated. In addition, fundamental wetting models were used to explain the experimental results obtained. SAP Al surfaces could see a wide range of applications in fields such as self-cleaning, anti-icing, anticorrosion, oil transportation, energy harvesting, and microfluidics.