DEVELOPMENT OF NEW ZINC BASE ALLOYS FOR BIODEGRADABLE IMPLANTS

The potential of Zinc base alloys to serve as structural material for biodegradable implants relates to their good biocompatibility and non-toxic corrosion products. The present study aims at evaluating the in vitro performance of two newly developed alloys: Zn-1%Mg and Zn-1%Mg-0.5%Ca. The alloys were prepared at 480°C and die casted using a cold chamber die casting machine with 180 ton clamping force. The microstructure was examined by optical microscopy, SEM and XRD analysis while the mechanical properties were tested using Vickers hardness measurements. The corrosion behavior was studied in terms of immersion test, potentiodynamic polarization and electrochemical impedance spectroscopy in PBS solution at 37°C and at room temperature. The results obtained indicate that the Zn-1%Mg contains two phases: Zn matrix and MgZn₂, while additions of 0.5%Ca to this alloy produce three phases: Zn, Mg₂Zn₁₁ and CaZn₁₃ with a lamellar structure in both cases. Furthermore the addition of Ca induced grain refinement and improves the mechanical properties. In terms of corrosion performance the addition of Ca improve the corrosion resistance and the homogeneity of the general corrosion processes.