Investigation of hybrid PEO coatings on AZ31B magnesium alloy in alkaline K2ZrF6–Na2SiO3 electrolyte solution

Detail study of the PEO coatings produced on AZ31B magnesium alloy in Na2SiO3–K2ZrF6-based electrolyte solution was carried out in this work. ZrO2, MgF2, MgO and Mg2SiO4 were observed as the major phases in the coatings. Electrolytic decomposition and then the severe thermochemical environment provoked various Zr–F–Mg based complexes in the coatings. From the surface analysis, various structures e.g, nano-grains, pores and volcano shape sintered material were evidenced. Using Vicker hardness test, maximum hardness was recorded as ~1280 HV. Potentiodynamic polarization technique in 3.5 wt % NaCl solution was used to predict the corrosion performances of the specimens. Among the coated samples, highest corrosion resistance was recorded to be ~223.5 × 103 kΩ/cm2 for 15 min coatings.