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

Abstract

Yttria stabilized zirconia ͑YSZ͒ coating was formed on an AZ31 Mg alloy by aerosol deposition ͑AD͒ 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 ͑EIS͒. The crack-free, dense, and ϳ4 m thick YSZ coating was successfully obtained by the AD method. The YSZ coating was polycrystalline and composed of ϳ10 nm nanocrystallites. The potentiodynamic test indicated that the YSZ coated AZ31 Mg alloy had a more positive corrosion potential ͑−1.39 V vs SCE͒, much lower corrosion current density ͑0.02 A/cm 2 ͒, and much higher polarization resistance ͑2500 k⍀ 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 ϳ10 7 ⍀ cm 2 at low frequencies, which was ϳ5 orders of magnitude higher than that of the uncoated Mg alloy. Furthermore, the high impedance ͑ Ͼ 10 6 ⍀ 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.

The effect of current mode and discharge type on the corrosion resistance of plasma electrolytic oxidation (PEO) coated magnesium alloy AJ62

“…The model chosen for the fitting was a commonly used model for PEO [15,16,41] and other ceramic coatings [42,43]. The choice of the circuit was a balance between a reasonable fitting of the experimental values and a good description of the electrochemical system by keeping the number of circuit elements at a minimum.…”

“…R S is the solution (electrolyte) resistance. R coat is the coating resistance (virtual pore resistance [42]) which is parallel with a constant phase element CPE1 (CPE coat in model of Ryu et al [42]). CPE2 is the constant phase element for the double layer capacitance of the interface electrical double layer at or near the coating/substrate interface.…”

Corrosion Performances Of Micro-Arc Oxidation Coatings On Az31B, Az80 And Zk60 Cast Mg Alloys

“…The proposed equivalent circuit of MAO coated Mg alloys is shown in Fig.5c. It consists of Rs, Rct and Qdl, coating resistance (Rcoat) and coating capacitance (Qcoat) which is the virtual properties of MAO coating [16]. It can be seen from Fig.4 that the simulated curves fit very well with the experiment data.…”

Tuning the Microstructure and Thickness of Ceramic Layers with Advanced Coating Technologies Using Zirconia as an Example

“…Crack‐free, dense YSZ coatings with thicknesses between 4 and 5 μm and more than 100 μm were successfully deposited by AD. They offer corrosion protection on aluminum [ 263 ] and magnesium alloys [ 264 ] to improve the surface hardness of stainless steel [ 265 ] or as electrolytes in NO x sensors. [ 266 ] In contrast to alternative porous, screen‐printed electrolytes, lower noise, and higher sensitivities toward NO, as well as NO 2 , were observed for the dense coatings obtained by AD.…”