Improving the Corrosion Resistance of Wrought ZM21 Magnesium Alloys by Plasma Electrolytic Oxidation and Powder Coating

Plasma Electrolytic Oxidation (PEO) was applied to extruded ZM21 Mg alloys improve their corrosion resistance in a chloride-containing environment. PEO carried out DC mode and voltage control fluoride-free electrolyte. Potentiodynamic polarization tests 3.5 wt.% NaCl aqueous solution neutral salt spray (NSS) were out. Microstructural profilometric characterization, as well NSS performed different conditions: (i) bare ZM21, (ii) PEO-treated (iii) powder-coated (without interlayer), (iv) with powder coating top layer (carboxyl-functionalized polyester resin). The + double identified the best-performing protection.