The effect of slow strain rate tension and cyclic loading on biodegradable Zn–2%Fe–0.8%Mn alloy in a simulated physiological environment

Abstract

Zinc-based alloys have gained increased interest as biodegradable structural materials for medical applications due to their adequate biocompatibility, crucial roles in many physiological functions and attractive antibacterial properties. However, the major drawbacks of zinc alloys relate to their inadequate mechanical properties and tendency to provoke fibrous encapsulation due to relatively high standard potential. Based on the promising effect of Mn on properties of Zn-based alloys, the present study aimed at evaluating the suitability of Zn–2%Fe–0.8%Mn alloy as a potential biodegradable implant under in-vitro conditions. This evaluation focused on the passivation characteristics as determined by cyclic potentiodynamic polarization analysis, immersion test, stress corrosion behavior by slow strain rate testing (SSRT), corrosion fatigue and direct cell viability in terms of cell adherence and proliferation after 24 and 48 h post incubation. The results showed that the addition of 0.8%Mn to the base Zn–2%Fe alloy improves the specific strength and direct cell viability characteristics while decreasing the effectiveness of natural passivation processes. The main overall effect of adding 0.8%Mn to Zn–2%Fe alloy were (i) reduced stress corrosion resistance in terms of time to failure at a low strain rate (2.5 × 10−7 s−1) from 285 h to 205 h (ii) reduced corrosion fatigue endurance from 4,997,285 cycles to only 377,552 cycles to failure at the lowest load of 30 MPa.

Keywords

• Biodegradable implants
• Cell viability
• In vitro
• Zinc
• Corrosion fatigue
• Slow strain rate testing