Abstract

Abstract The plasma electrolytic oxidation (PEO) technique was used to coat AZ31 magnesium alloy in a phosphate-based electrolyte. Effects of oxidation time on the morphology, phase structure, and corrosion resistance of the ceramic coatings were systematically investigated by scanning electron microscopy, X-ray diffraction, potentiodynamic polarization and electrochemical impedance spectroscopy testing. The main components of the resulting coatings were MgO, MgF2 and t-ZrO2. It was also found that there was a significant influence of the oxidation time on the corrosion resistance of the coatings. The coating obtained under the oxidation time of 10 min exhibited a corrosion current of 3.89 × 10−6 A cm−2 in 3.5 wt.% NaCl solution, which was a significant decrease compared with the uncoated magnesium alloy. The results of the corrosion tests indicated that the PEO coating formed at 10 min demonstrates a higher corrosion resistance compared to the samples formed at 5, 15 and 20 min.

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