The Effect of Applied Voltage and Mg Content of the Substrate on the Microstructure and Corrosion Performance of the Anodized Al with PEO Technique

Plasma electrolytic oxidation (PEO) technique was used to prepare ceramic coatings on the casted aluminum alloys containing ~5 and ~9.5 wt.% Mg. The applied voltage was controlled at 450V and 550V for evaluating the effect of this main parameter, as well as, magnesium content of the substrate on the microstructure and electrochemical corrosion behavior after PEO treating. The results of X-ray diffraction confirmed formation of galumina and MgSiO3. It was found that higher applied voltage caused fewer and minor discharge channels which led to higher corrosion resistance. Also, increasing of magnesium content of the substrate caused decreasing of polarization resistance, which could be associated to the formation of MgSiO3.