Peridynamic modeling of uniform and pitting corrosion in Mg-based bio-absorbable orthopedic screws

In this paper the dissolution process of bio-absorbable fixation screws is modeled using a Peridynamic approach, taking into account both uniform and non-uniform degradation pathways and comparing the resulting behaviors. Leveraging the FFT-accelerated Perifast/Corrosion code, its original, constant corrosion current implementation is extended by introducing a phenomenological space and time dependent corrosion current density field defined on the computational nodes. This allows for a consistent description of the localized anodic hotspots associated with pitting-like roughening on the corroding solid/liquid interface. The selection of material parameters either from experimental data or from numerical tuning allows the investigation of the degradation of a Magnesium alloy screw immersed for 60 days in an electrolyte mimicking physiological fluids. The numerical simulations reproduce the characteristic regimes of volume loss evolution, and provide valuable insight into complementary degradation metrics. Finally, the model is demonstrated on an implanted screw configuration, simulating exposure to the different layers of bone tissue. The results highlight the potential of the proposed framework for future multifield models coupling corrosion, mechanics and bone remodeling.