The mechanism of deposition of calcium phosphate coatings from solution onto magnesium alloy AZ31

In recent years, magnesium alloys have been proposed as a new class of metallic bioabsorbable implant material. Unfortunately, hydrogen gas evolution and an increase in alkalinity are both byproducts of the degradation process. This necessitates the development of magnesium alloys with controlled degradation rates. The development of biocompatible coatings that can delay the onset of corrosion is essential for improving the lifetime and performance of these materials ill vivo. Calcium phosphate coatings have been shown to improve the biocompatibility of metallic implants for orthopedic applications. In this article, we report a solution chemistry technique for depositing calcium phosphate coatings on magnesium alloy surfaces. Our kinetic Studies indicate that the deposition of the coating is related to the anodic dissolution Of the substrate. Characterization of the coating by XPS, SEM/EDS, and XRD reveal that the coating produced is a poorly crystalline calcium magnesium hydroxyapatite material. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 90A: 339-350, 2009