Influence of electrolyte composition on corrosion properties of PEO coating prepared on EV31 magnesium alloy

This paper deals with the influence of electrolyte composition on the corrosion properties of plasma electrolytic oxidation coating prepared on EV31 magnesium alloy. An electrolyte for PEO was prepared with 12 g of Na3PO4 and different amounts of KOH (1, 2, and 4 g). PEO coating was prepared using a DC regime with a constant current density of 50 mA.cm−2. Voltage and time dependence was recorded with BenchVue software. The time to achieve initial dielectric breakdown and the initial dielectric breakdown voltage decreased with increasing content of KOH. Corrosion resistance was evaluated using potentiodynamic polarization after one hour of exposition in 0.1 M NaCl. There was no significant difference in thermodynamical stability among samples fabricated in electrolytes with different KOH contents. The lowest corrosion current density value (1.82 mA.cm−2) was achieved by adding 2 g/l of KOH to the electrolyte.