Tuning of the Mg Alloy AZ31 Anodizing Process for Biodegradable Implants
Andrea Zaffora, Francesco Di Franco, Danilo Virtù, Francesco Carfì Pavia, Giulio Ghersi, Sannakaisa Virtanen, Monica Santamaria
Abstract
Coatings were grown on the AZ31 Mg alloy by a hard anodizing process in the hot glycerol phosphate-containing electrolyte. Anodizing conditions were optimized, maximizing corrosion resistance estimated by impedance measurements carried out in Hank’s solution at 37 °C. A post anodizing annealing treatment (350 °C for 24 h) allowed us to further enhance the corrosion resistance of the coatings mainly containing magnesium phosphate according to energy-dispersive X-ray spectroscopy and Raman analyses. Gravimetric measurements revealed a hydrogen evolution rate within the limits acceptable for application of AZ31 in biomedical devices. In vitro tests demonstrated that the coatings are biocompatible with a preosteoblast cell line.