Microstructure and corrosion resistance of ultrasonic micro-arc oxidation biocoatings on magnesium alloy

Lijie Qu,Miao Liu,Chen Ma,Erlin Zhang,Muqin Li

doi:10.1007/s40145-013-0064-y

Abstract

The ultrasonic micro-arc oxidation (UMAO) was used to fabricate ceramic coatings on magnesium alloy. UMAO coatings were produced at 60 W input ultrasonic. The effects of the ultrasound on the microstructure, phase composition, elemental distribution and corrosion resistance of the coatings were extensively investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX) and electrochemical workstation. The results showed that ultrasound improved the homogeneous distribution of micro-porous structure. The coatings were mainly composed of MgO ceramic and small amount of calcium and phosphorus with porous structure. The Ca/P ratio of the coatings increased when 60 W ultrasonic was used. The corrosion potential in simulated body fluid (SBF) changed from −1.583 V of bare magnesium alloy to −0.353 V of magnesium alloy coated under 60 W ultrasonic. The corrosion resistance of UMAO coatings was better than that of MAO coatings.

Highlights

Magnesium and its alloys have been investigated as implants for almost two centuries due to the advantages and obvious benefits from biodegradable metal implants [1,2]; commercial implants containing magnesium and its alloys are still not available until now
The porous microstructure of micro-arc oxidation (MAO) ceramic coatings would result in an increase in corrosion rate of magnesium alloys
MAO combined with other methods was used to improve the corrosion resistance of magnesium alloys and the biocompatibility of MAO coatings

Summary

Introduction

Magnesium and its alloys have been investigated as implants for almost two centuries due to the advantages and obvious benefits from biodegradable metal implants [1,2]; commercial implants containing magnesium and its alloys are still not available until now. Electro-deposition was used to fabricate a top layer of DCPD on AZ80 Mg alloy coated by MAO to improve the corrosion resistance and bioactivity [23]. These composite methods need two steps, though the corrosion resistance of magnesium alloy and the bioactivity of MgO layer were improved . The minimum ultrasonic power density was applied during the MAO process to fabricate ultrasonic micro-arc oxidation (UMAO) coatings on magnesium alloy to develop a one-step method to improve corrosion resistance of magnesium alloy and make the excellent biological performance of UMAO coatings. The microstructure and corrosion resistance properties of UMAO coatings were studied

Experiment

Results and discussion

Conclusions