Corrosion Protective Film Formation on Mg Alloys AZ 31 by Exposure to Dilute Selenite Solutions
Zhiyuan Feng1,2,3, Charles C Xu2, Dadi Zhang2
1School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China.
Abstract:
The study of protective film formation on Mg alloys by exposure to sodium selenite solutions was conducted. Anodic polarization studies, electrochemical impedance spectroscopy studies, morphological analysis, and Energy-dispersive X-ray spectroscopy were performed on AZ31 Mg alloy after coating treatment in different concentrations of sodium selenite. The corrosion resistance was improved by around 5 times compared with control. Improved resistance to localized corrosion was observed in the coatings treated by 5 mM or 10 mM sodium selenite. The protection mechanism was ascribed to the transformation of selenite to insoluble selenium, the formation of insoluble MgSeO3 hydrate, and polymerization of amorphous selenium.
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