Study On Preparation And Properties Of Superhydrophobic Composite Coating On Magnesium Alloy

Magnesium alloy has many advantages, known as the green metal in twenty-first Century, but its chemical properties are very lively, easy to corrosion, therefore, magnesium alloy should carry out surface preparation in order to be widely used. The traditional surface treatment methods have different drawbacks, more and more composite coatings are widely used because of it is a combination of the advantages of each surface treatment method, so it can strengthen its comprehensive performance, and make the magnesium alloy has been more widely used.In this paper, we proposed a new surface treatment method of magnesium alloy, it accepts the nicke coating as the bottom, free-chrome zinc aluminum coating as the surface,attached a layer of SiO₂ nanoparticles in the above. The super hydrophobic composite coating combines the wear resistance of the plating layer, the salt spray resistance of the free-chrome zinc aluminum coating, the super hydrophobic of SiO₂ nano particles, make themagnesium alloy equipped a kind of wear and corrosion resistance and self-cleaning effect.The surface morphologies, structure and compositions of the nickel plating on magnesium alloy, free-chrome zinc aluminum coating and super hydrophobic composite coating were investigated by SEM, Laser confocal, XRD and FTIRI respectively; the hydrophilic and hydrophobic effect of the super hydrophobic composite coating were characterized by contact angle instrument and surface tension meter. Then according to the international standard test method test sthe coating adhesion for different kinds of coatings on each layer, the corrosion resistance of the coating were analyzed by electrochemical workstation and salt spray test methods. The results show that the super hydrophobiccomposite coating has excellent adhesive force, the roughness were reduced because of the nano-particles SiO₂ did enter into those defects of the chromium-free Zn-Al coating and enable it to have the good superhydrophobicity, self-cleaning effect; the corrosion test shows that the comprehensive corrosion effect is the best.