A novel combination of electrical discharge machining and electrodeposition for superamphiphobic metallic surface fabrication

A superamphiphobic surface is prepared on aluminum substrate by combination of electrical discharge machining (EDM) and electrodeposition. The micro-scale pit structures obtained after EDM were used as a pretreatment method to electrodeposit Zn nanoparticles on this surface, then fluoro-silanization assembled TiO2 (TiO2-FAS) reduced surface energy, finally we obtained a superamphiphobic surface. The contact angle (CA) of the water droplets reaches 169.8 +/- 3.0 degrees, and that of oil droplets reaches 154.5 +/- 8.3 degrees on this surface. This as-prepared surface has a hierarchical micro-nanostructure, and EDM treatment improves its mechanical stability, since the surface was verified to maintain a large CA after long distance abrasion. The high-speed camera was used to observe the water and oil droplets bounce during impact, which demonstrates excellent water and oil repellence. A drag reduction test equipment was built according to pressure differential theory, and it was verified that the flow resistance on the as-prepared surface decreased relative to bare Al substrate. Self-cleaning performance test was carried out. Based on this fabrication method, we took the advantages of EDM in metal to obtain superamphiphobic patterns and curve surfaces, such as ball sockets and inner surface of holes. The approach broadens the application of EDM and enriches the fabrication on superhydrophobic surface.