Effect of (NH<sub>4</sub>)<sub>2</sub>ZrF<sub>6</sub>, Voltage and Treating Time on Corrosion Resistance of Micro-Arc Oxidation Coatings Applied on ZK61M Magnesium Alloys

oleh: Jiahui Yong, Hongzhan Li, Zhengxian Li, Yongnan Chen, Yifei Wang, Juanjuan Geng

Format: Article
Diterbitkan: MDPI AG 2021-12-01

Deskripsi

The effects of (NH<sub>4</sub>)<sub>2</sub>ZrF<sub>6</sub> concentration, voltage and treating time on the corrosion resistance of ZK61M magnesium alloy micro-arc oxidation coatings were studied by orthogonal experiments. The SEM result shows that the surface roughness and porosity of MAO coatings increased with (NH<sub>4</sub>)<sub>2</sub>ZrF<sub>6</sub> concentration, voltage and treating time as a whole, except the porosity decreased with treating time. EDS, XRD and XPS analysis show that (NH<sub>4</sub>)<sub>2</sub>ZrF<sub>6</sub> was successfully incorporated into coatings by reactive incorporation, coatings are dominantly composed of ZrO<sub>2</sub>, MgO, MgF<sub>2</sub> and amorphous phase Mg phosphate. Potentiodynamic polarization was used to evaluate the corrosion property of coatings. When the concentration of (NH<sub>4</sub>)<sub>2</sub>ZrF<sub>6</sub> is 6 g/L, the voltage is 450 V, and the treating time is 15 min, the coating exhibits the best corrosion resistance which corrosion current density is four magnitudes lower than substrate attributed to the incorporation of ZrO<sub>2</sub> and the deposition of MgF<sub>2</sub> in the micropores.