Abstract
In this study, ceramic coatings were deposited on AZ31 magnesium alloy by micro arc oxidation (MAO) technique in sodium phosphate electrolytes (Na3PO4.12H2O) containing different concentrations of sodium hydroxide (NaOH) and borax (Na2B4O7) under voltage of 420 V for 5 min. Hank’s solution was used to investigate the corrosion behavior of the samples. Potentiodynamic polarization and electrochemical impedance spectroscopy were also employed. X-ray diffraction and scanning electron microscopy were applied for phase and microstructure characterization. The prepared MAO layers consisted mainly of ZnO and Mg3PO4. Results indicated that use of micro arc oxidation technique for coating may result in significant increase of corrosion resistance of magnesium alloy in Hank’s solution. One of the important parameters which affects this coatings properties is the electrolyte composition which used in the process. The coating deposited by application of 10 g/l Na3PO4 + 1.5 g/l NaOH, exhibited the highest corrosion resistance in Hank’s solution among the samples.
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