Electrochemical Corrosion Properties of Nanostructured YSZ Coated AZ31 Magnesium Alloy Prepared by Aerosol Deposition

Abstract

Yttria stabilized zirconia 共YSZ兲 coating was formed on an AZ31 Mg alloy by aerosol deposition 共AD兲 at room temperature, and its electrochemical corrosion properties were investigated in 3.5 wt % NaCl solution by potentiodynamic polarization test, poten- tiostatic test, and electrochemical impedance spectroscopy 共EIS兲. The crack-free, dense, and ⬃4 ?m thick YSZ coating was successfully obtained by the AD method. The YSZ coating was polycrystalline and composed of ⬃10 nm nanocrystallites. The potentiodynamic test indicated that the YSZ coated AZ31 Mg alloy had a more positive corrosion potential 共−1.39 V vs SCE兲, much lower corrosion current density 共0.02 ?A/cm2兲, and much higher polarization resistance 共2500 k⍀ cm2兲 in comparison to an uncoated Mg alloy. The pitting corrosion was observed in the YSZ coated Mg alloy, and the determined pitting potential 共Eb兲 was close to −0.8 V vs SCE. EIS results demonstrated that the impedance of the YSZ coated Mg alloy was ⬃107 ⍀ cm2 at low frequencies, which was ⬃5 orders of magnitude higher than that of the uncoated Mg alloy. Furthermore, the high impedance 共 ⬎ 106 ⍀ cm2兲 of the YSZ coated Mg alloy was still maintained after 120 h immersion in 3.5 wt % NaCl solution. Consequently, the corrosion resistance of the AZ31 Mg alloy was significantly improved by the AD YSZ coating. © 2010 The Electrochemical Society. 关DOI: