Magnetic energy drives mass transfer processes to accelerate the degradation of Fe-based implant

Abstract

The main obstacle of Fe towards the orthopedic application is the slow degradation rate. In this work, a FeGa alloy is developed by mechanical alloying and selective laser melting, and exposed to magnetic field to investigate the influence of magnetic energy on the degradation behavior of the alloy. The magnetic field magnetizes the FeGa alloy and establishes an induced magnetic field, which forms gradient magnetic energy around the corrosion pits during the degradation period. The gradient magnetic energy transfers the paramagnetism corrosion product particles like FexOy and GaOx to the edge of the corrosion pits and avoids the deposition of passive corrosion product layer, thereby maintaining the erosion of immersion solution to achieve a continuous corrosion process. Moreover, the magnetic field subjects Lorentz forces to oxygen and the corrosive ions in the medium, which provides driving forces for transferring them to the alloy surface, thereby accelerating the oxygen absorption degradation reaction. Results indicate that FeGa alloy coupled with magnetic field has a smaller charge transfer resistance of 3297.8 Ω than FeGa alloy (4877.2 Ω) and Fe (5951.1 Ω) in the absence of magnetic field, indicating a lower corrosion resistance of the corrosion product layer. Furthermore, the FeGa alloy in magnetic field exhibits high corrosion current density of 28.12 ± 0.35 μA/cm2 and fast corrosion rate of 0.25 ± 0.02 mm/year, which are significantly higher than FeGa alloy and Fe without magnetic field. The findings of this work suggest that combining component design with external field interactions can effectively regulate the degradation of Fe-based implants.