Abstract:

A hierarchical roughness was fabricated on brass surface by chemical etching with a FeCl₃-HCl-H₂O solution. The roughness consisted of irregular pieces and fine papilla. After fluorination treating，the brass surface exhibited super-hydrophobic properties，with a water contact angle of about 157° and contact angle hysteresis of about 5°. The effect of etching time on the hydrophobicity of the surfaces was investigated. The results indicated that the etching time played an important role in the formation of hierarchical roughness and of a high contact angle. With the increase of etching time，the hierarchical structure gradually formed on the surface and the contact angle gradually increased until a constant value was reached. The contact angle hysteresis decreased as the contact angle increased. The possible mechanism of the formation of hierarchical roughness was proposed. Also，the wettability of brass surface was discussed on the basis of the Cassie theory.