Preparation and Properties of Environmental Zinc/Aluminum Based Corrosion Resistant Coating

To replace the traditional chrome dacromet coating,an environmental and chrome-free zinc/aluminum based corrosion resistant coating was prepared on 20 steel using silane as binder and flaky zinc/aluminum powders as raw materials.The composition and structure of the coating were characterized by X-ray diffraction and scanning electron microscopy.The electrochemical behavior and corrosion properties of the coating were investigated by open-circuit potential measurement,electrochemical impedance spectroscopy and salt spray test.The results indicate that the corrosion resistance of the chrome-free coating was nearly the same to that of the traditional chrome dacromet coating.It was also showed that silane only played an adhesive role in the coating and the flaky zinc and aluminum powders were uniformly distributed and stacked in the coating.Cathodic protection and shielding effects were the main means employed to protect the matrix metal against corrosion,and the shielding effect was increased with the increase of the coating thickness.