113 / 2021-04-02 15:14:06

Improved corrosion resistance of AZ91D magnesium alloy coated by novel cold-sprayed Zn-HA/Zn double-layer coatings

HA/Zn; Cold spraying;,Corrosion resistance

In order to improve the corrosion resistance and bioactivity of biodegradable Mg alloy substrate, novel Zn-HA/

Zn double-layer coatings with different HA/Zn ratios in weight were deposited on AZ91D substrates by cold

spraying. Phase compositions and microstructures of as-sprayed coatings and coatings after corrosion tests were

analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron

microscopy (SEM). Electrochemical corrosion behaviors of both Zn-HA/Zn double-layer coatings were investigated

in Hanks’ simulated body fluid using potentiodynamic polarization and electrochemical impedance

spectroscopy (EIS). Results showed that both the pure Zn coating and HA/Zn composite coatings presented the

similar phase compositions with their primary powders in addition to Zn oxidizations. Zn powders were plastically

deformed and partially oxidized due to its low melting point, while HA powders were mainly crashed into

fragments and hill-like splats. Both Zn under layer and HA/Zn upper layer were well bonded and presented dense

structures, differences in HA/Zn upper layers were related to the HA/Zn ratios. Potentiodynamic polarization

and EIS measurements illustrated that the cold-sprayed Zn-HA/Zn double-layer coatings not only improve the

corrosion resistance of Mg alloy substrates, but also enhance its bioactivity due to the HA existed in composite

upper layer.