Surface modification of Mg95Zn4.3Y0.7 alloy powder consolidates by plasma electrolytic oxidation

Abstract

This work investigates the microstructure and corrosion resistance of the oxide layer on Mg95Zn4.3Y0.7 alloy powder consolidates prepared by plasma electrolytic oxidation (PEO). The oxide layers on the Mg95Zn4.3Y0.7 alloy samples exhibited surface morphology typical of bulk Mg and Mg alloys treated using the PEO process, regardless of the thickness of the layer. The polarization resistance of the oxide layer increased as the thickness of the layer increased. The best corrosion resistance was obtained for the sample with a 30 mu m oxide layer. All samples were produced using an electrolyte containing K4P2O7. A reasonable equivalent circuit to analyze the corrosion behavior of Mg95Zn4.3Y0.7 alloy was established, and the fitting results were consistent with the results of electrochemical impedance spectroscopy (EIS) testing. These results explain the relationship of enhanced corrosion resistance to the thickness of oxide layer in environments containing Cl- ions. (C) 2010 Elsevier B.V. All rights reserved.