MICROSTRUCTURAL CHANGES OF THE PEO COATING INDUCED BY SILANE-BASED SOL–GEL TREATMENT

In this paper, the silane-based sol–gel treatment process was applied to the plasma electrolytic oxidation (PEO) ZM6 Mg-alloy. The microstructural characteristics and corrosion resistance of the PEO/organic composite coatings were studied by means of SEM and XRT in conjunction with electrochemical measurements. The results showed that the microdefects in the PEO coating could be effectively filled with the silane compounds, reducing the porosity of the PEO coating. The treated PEO coating had a hydrophobic property, which may be related to the siloxane network (Si–O–Si) formed on the PEO coating surface. The corrosiveness of the silane agent to the PEO coating and the generation of internal stress in the PEO coating resulted in the damage of microstructures of the PEO coating. The global and local electrochemical measurements showed that the corrosion-resistant performance of the PEO Mg-alloys after the silane-based sol–gel treatment was improved and its service life would be shortened by the balance of micropores without sealing and the damaged microstructure.