Aerosol deposition of hydroxyapatite–chitosan composite coatings on biodegradable magnesium alloy

Magnesium (Mg) and its alloys are potential biometallic materials for their good biocompatibility and excellent biological performances. However, Mg alloys corrode too quickly in chloride containing solutions, including the human body fluid and blood plasma, which may result in the abrupt failure of implants made of Mg alloys. Dense and well-adherent HA–chitosan composite coatings were deposited on AZ31 Mg alloy substrate using aerosol deposition (AD) in order to improve both the corrosion resistance and biocompatibility of AZ31 Mg alloy. The HA–chitosan composite powders having chitosan contents of up to 20 wt.% were prepared by a simple dry-powder mixing process and then used for coating by AD. The coatings obtained from the corresponding powders were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and electrochemical measurement. The results revealed that the coating layers had similar compositions to the corresponding powders and exhibited fairly dense microstructures and, hence, AD was found to be a very effective method for the fabrication of dense ceramic–polymer composite coatings with a well-controlled composition. All of the coatings exhibited high adhesion strengths ranging from 24.6 to 27.7 MPa and showed higher corrosion resistances than the bare AZ31 Mg substrate, implying that the corrosion resistance of AZ31 Mg alloy is enhanced by the HA–chitosan composite coating deposited using AD. In addition, the biocompatibility of the alloy was remarkably improved by the HA coating and the incorporation of chitosan into the coating.