Study of Coating Growth Behavior During the Plasma Electrolytic Oxidation of Magnesium Alloy ZK60

Plasma electrolytic oxidation technique was used to coat ZK60 magnesium alloy in a silicate-based electrolyte. Effects of oxidation time on the morphology, phase structure, and corrosion resistance of the resulting coatings were systematically investigated by scanning electron microscopy, energy-dispersive spectrometry, x-ray diffraction, x-ray photoelectron spectroscopy, and potentiodynamic polarization. The main components of the inner and the outer coating layers were MgO and Mg2SiO4, respectively. It was also found that the oxidation time has a significant impact on the corrosion resistance properties of the coatings. The coating obtained within the oxidation time of 360 s exhibited a corrosion current of 7.6 x 10(-8) A/cm(2) in 3.5 wt.% NaCl solution, which decreased significantly when comparing with the pristine magnesium alloy.