Fabrication and characterization of dicalcium phosphate coatings deposited on magnesium substrates by a chemical conversion route

It is well established that magnesium (Mg) is a promising material for use in biomedical applications. Nonetheless, it exhibits an accelerated corrosion rate when present in physiological media, which may lead to premature degradation of the implant in the body. As a result, it is necessary to slow down the corrosion of Mg in order to ensure that the implant is able to maintain its mechanical integrity during the whole healing period. In this work, dicalcium phosphate dihydrate (DCPD) coatings were formed on hot-rolled Mg substrates by a chemical conversion route aiming to increase the corrosion resistance and biointegration of the latter. The materials prepared herein were examined by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, electrochemical impedance spectroscopy, and in vitro assays. The sample obtained after immersing Mg in the phosphating bath for 24 h and with no heat treatment was the one with the highest corrosion resistance. This sample also exhibited the formation of a hydroxyapatite layer on its surface after soaking in Hank's balanced salt solution for times as short as 1 day. Moreover, this specimen showed no toxicity to rat mesenchymal stem cells, suggesting that it is a promising material for biomedical applications.