3 - Chemical solution deposition of hydroxyapatite and octacalcium phosphate coatings for magnesium and its alloys to improve biocompatibility

Abstract

Well-crystallised hydroxyapatite (HAp) and octacalcium phosphate (OCP) were directly coated on Mg/Mg alloys with a novel chemical solution deposition method using a Ca-chelate compound to control corrosion resistance and to improve the biocompatibility of Mg/Mg alloys. Influence of coating treatment conditions (temperature, pH, etc.) on the coatings was examined. Microstructure and composition of the coatings were precisely analysed using X-ray diffraction, Field emission-secondary electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform-infrared spectroscopy. Long-term corrosion behaviour and short-term biocompatibility of the coated Mg alloy were examined with immersion and cell-culture tests, respectively. Adhesiveness of the HAp coating was investigated under static tensile and fatigue loadings. Fatigue behaviour of the HAp-coated Mg alloy was examined in air. The HAp and OCP coatings could control the corrosion rate of the Mg alloy. Fatigue strength of the Mg alloy was not remarkably influenced with the HAp coating. The HAp coating showed excellent adhesiveness under the fatigue loading. The chemical solution deposition method is introduced, and advantageous properties of the HAp- and OCP-coated Mg alloy are discussed.