Microstructure of hydroxyapatite-coated magnesium prepared in aqueous solution

Hydroxyapatite (HAp) coatings were directly formed on pure magnesium in aqueous solutions using C10H12CaN2Na2O8 (Ca-EDTA) and KH2PO4. The influence of the treatment temperature and concentration of Ca-EDTA on the microstructure of the coatings was investigated. The growth of the HAp crystals was promoted with an increase in the treatment temperature. The growth direction of HAp crystals was along [002]HAp regardless of the treatment temperature, and the HAp crystals then showed a rod-like shape. The HAp crystals contained Na and Mg. A Mg(OH)2 layer was formed between the HAp coating and the magnesium substrate above 363 K. With a decrease in the treatment time, the formation of the Mg(OH)2 layer was suppressed. A dense and uniform HAp-coating layer was obtained without the formation of a Mg(OH)2 intermediate layer by adjusting the treatment time and concentrations of calcium and phosphate species.