Preparation and characterization of a composite coating composed of polycaprolactone (PCL) and amorphous calcium carbonate (ACC) particles for enhancing corrosion resistance of magnesium implants

Abstract

Magnesium (Mg) and its alloys serve as potential biodegradable implants material because of their excellent biocompatibility and appropriate biomechanical compatibility. However, the high degradation rate in vivo limits the practical applications of magnesium based materials. To improve the corrosion resistance of Mg alloy, a uniform composite coating of polycaprolactone (PCL) and amorphous calcium carbonate (ACC) particles was prepared on AZ60 by dip-coating. Results of electrochemical measurements and immersion tests in SBF solution suggested that the composite coating remarkably improved the corrosion resistance of AZ60 alloy. The increase in corrosion resistance by the composite coating protection can be ascribed to two factors: (i) an initial barrier to delay the ingress of SBF solution, (ii) the gradual dissolution of ACC particles and release of phosphate ions to form a Mg phosphate layer, which protects the Mg substrate. In addition, the microstructure and composition for the composite coating after immersion showed that massive Mg modified ACC and apatite precipitates formed on the surface, which is indicative of its superior biomineralization capability. In summary, this PCL/ACC composite is a promising coating material for tailoring the degradation behavior of magnesium for orthopedic applications.