Microstructure and properties of the super-hydrophobic films fabricated on magnesium alloys

A simple and efficient method for fabricating a super-hydrophobic film on magnesium alloys has been developed using chemical silvering and self-assembly treatments. The treated magnesium alloy surface exhibits high hydrophobicity with an apparent contact angle of 153° and contact angle hysteresis of 4°. The super-hydrophobic film is covered with serried and uniform micro-spherical structures which are composed of irregularly arranged nano-plates. The micro-nano hierarchical structures can trap air to form an extremely thin layer of air cushion between water and the film, and the air cushion is crucial for the super-hydrophobility of the film. The super-hydrophobic phenomenon of the prepared film was analyzed with Cassie theory, and the analysis revealed that only about 15% of the water contact surface is contacted with the metal substrate and the rest 85% is contacted with the air cushion. Comparing with untreated magnesium alloys, the corrosion resistance of treated magnesium alloy in 0.1 mol/L NaCl aqueous solution is significantly improved by the super-hydrophobic film, and the film is positive enough to prevent the pitting corrosion.