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

Yttria stabilized zirconia (YSZ) coating was formed on an AZ31 Mg alloy by aerosol deposition (AD) at room temperature, and its electrochemical corrosion properties were investigated in 3.5 wt % NaCl solution by potentiodynamic polarization test, potentiostatic test, and electrochemical impedance spectroscopy (EIS). The crack-free, dense, and similar to 4 mu m thick YSZ coating was successfully obtained by the AD method. The YSZ coating was polycrystalline and composed of similar to 10 nm nanocrystallites. The potentiodynamic test indicated that the YSZ coated AZ31 Mg alloy had a more positive corrosion potential (-1.39 V vs SCE), much lower corrosion current density (0.02 mu A/cm(2)), and much higher polarization resistance (2500 k Omega cm(2)) in comparison to an uncoated Mg alloy. The pitting corrosion was observed in the YSZ coated Mg alloy, and the determined pitting potential (E-b) was close to -0.8 V vs SCE. EIS results demonstrated that the impedance of the YSZ coated Mg alloy was similar to 10(7) Omega cm(2) at low frequencies, which was similar to 5 orders of magnitude higher than that of the uncoated Mg alloy. Furthermore, the high impedance (> 10(6) Omega cm(2)) 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. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3525271] All rights reserved.