Influence of Complex SiF62- Ions on the PEO Coatings Formed on Mg-Al6-Zn1 Alloy for Enhanced Wear and Corrosion Protection

Abstract

The present study was carried out to explore the effect of SiF62- incorporation and concentration on the plasma electrolytic oxidation (PEO) coatings formed on AZ61 Mg alloy. The coatings were prepared using electrolyte solution with various concentration of Na2SiF6 (0.0-0.7 g/L). Highly compact coatings with minimum porosity were obtained for an optimum concentration of Na2SiF6 similar to 0.3 g/L added into the electrolyte. The highest corrosion resistance, similar to 2.04 x 10(5) ohm cm(2), was obtained for 0.3 g/L of Na2SiF6, in addition to its superior anti-wear properties. However, it was found from the scanning electron microscope (SEM) image analysis that increasing concentration above 0.3 g/L, could cause severe breakdown in the inner layers, and thus the said coatings could not withstand effectively against wear and corrosion.