Surface Characterization of AZ31 Alloy after Long-Term Immersion in Simulated Body Fluid

The aim of the research campaign was to simulate in vitro the typical conditions for the corrosion in biofluid of a femoral bone implant manufactured with AZ31 alloy. The samples were immersed in biofluid (alpha-MEM) for time intervals of up to 56 days. For each immersion time, the chemical compositions and morphologies of the samples were studied with SEM, EDX, XRD, Raman spectroscopy, and XPS. The weight losses of the samples caused by corrosion were also measured. The results highlighted the formation of calcium phosphate crystals on the surface of the samples. This type of coating is well-known for its excellent corrosion resistance and for its ability to accelerate tissue regeneration. The deceleration of the corrosion process, observed after 28 days of immersion in biofluid, confirms the anti-corrosive effect of the coating that was spontaneously formed during the immersion tests.