Surface modifications of biodegradable AZ31 alloy after immersion in physiological solution

Internal prosthesis and grafts are currently made of Ti alloys, stainless steels and Co-Cr alloys. In spite of excellent biocompatibility, they show some drawbacks that concern their mechanical properties (e.g. elastic modulus) and the need of secondary surgery for removing the implant. For this reason, a growing attention has been focused on biodegradable materials that can be absorbed into the body after tissue remodelling. In particular, Mg alloys are promising candidates for temporary implants thanks to their high biocompatibility, biodegradability and good mechanical properties that match those of human bone. In this work, the surface modifications of biodegradable AZ31 alloy were analysed after immersion for 15 days in a physiological solution (NaCl 0.09%) by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. XPS analysis of the surface of as-supplied AZ31 alloy showed the presence of MgO, whereas after immersion in the physiological solution, only Mg (OH)(2) was detected. The result has been discussed with reference to literature data. From the photoemission spectra and quantitative analysis, a small amount of Ca (about 2 wt%) was also detected.