Investigation of the Structural and Corrosion Properties of Duplex Surface Treated AZ31 Magnesium Alloy

The AZ31 alloy was first completely coated with pure aluminum in this study using the electric arc spray coating method. Then, considering the existing benefits of the micro-arc oxidation process (MAO), a ceramic oxide coating was formed by applying MAO to the Al-coated surface. Thus, a duplex coating was obtained on the base material. The structural properties of both the Al-coated samples and the duplex coatings obtained after the MAO process were investigated by scanning electron microscopy, energy-dispersive x-ray analysis (EDS), and x-ray diffraction devices. The electrochemical behavior of the coatings was carried out in a 3.5 wt.% NaCl solution. The samples were polarized from the potential value − 0.2 V below the corrosion potential to the maximum value of 2 V at a scanning rate of 1 mV/s, and potentiodynamic polarization curves were recorded. According to the electrochemical experiments, Al coatings and duplex coatings improved the corrosion resistance of AZ31 alloy. The corrosion current density values ​​were 298.23 µA/cm2 for the base material, 0.415 µA/cm2 for the Al coating, and 0.014 µA/cm2 for the duplex coating, respectively. The best corrosion resistance among all samples was obtained in duplex-coated samples obtained by MAO. Due to their low corrosion resistance, magnesium alloys are restricted in many areas, especially aviation, automotive, and biomedical. Therefore, this study aimed to improve the corrosion resistance of AZ31 magnesium alloy.