Wettability and drag reduction of a superhydrophobic aluminum surface

The present work reports a simple method to fabricate aluminum superhydrophobic surface using a two-step procedure, chemical etching and anodization. By varying the chemical etching and anodization time, we measured and compared the effects of morphological change on the wettability. The results indicate that the morphology is directly correlated to the wettability and adhesion ability. The resultant structure after the first step exhibits high adhesion properties. The high adhesion to low adhesion transition takes place after the anodization on the etched aluminum surface. The paper studies the effect of the adhesion on the liquid/solid friction drag. It is found that the adhesion has an obvious effect on friction drag. The drag reduction ratio for the low adhesion aluminum is about 50-60% compare with the high adhesion aluminum at low velocity. Such a property can be extensively used in the drag reduction field.