Phase-field modeling of pitting and mechanically-assisted corrosion of Mg alloys for biomedical applications

A phase-field model is developed to simulate the corrosion of Mg alloys in body fluids. The model in-corporates both Mg dissolution and the transport of Mg ions in solution, naturally predicting the tran-sition from activation-controlled to diffusion-controlled bio-corrosion. In addition to uniform corrosion, the presented framework captures pitting corrosion and accounts for the synergistic effect of aggressive environments and mechanical loading in accelerating corrosion kinetics. The model applies to arbitrary 2D and 3D geometries with no special treatment for the evolution of the corrosion front, which is de-scribed using a diffuse interface approach. Experiments are conducted to validate the model and a good agreement is attained against in vitro measurements on Mg wires. The potential of the model to capture mechano-chemical effects during corrosion is demonstrated in case studies considering Mg wires in ten-sion and bioabsorbable coronary Mg stents subjected to mechanical loading. The proposed methodology can be used to assess the in vitro and in vivo service life of Mg-based biomedical devices and optimize the design taking into account the effect of mechanical deformation on the corrosion rate. The model has the potential to advocate further development of Mg alloys as a biodegradable implant material for biomedical applications. Statement of significance A physically-based model is developed to simulate the corrosion of bioabsorbable metals in environments that resemble biological fluids. The model captures pitting corrosion and incorporates the role of mechan-ical fields in enhancing the corrosion of bioabsorbable metals. Model predictions are validated against dedicated in vitro corrosion experiments on Mg wires. The potential of the model to capture mechano-chemical effects is demonstrated in representative examples. The simulations show that the presence of mechanical fields leads to the formation of cracks accelerating the failure of Mg wires, whereas pitting severely compromises the structural integrity of coronary Mg stents. This work extends phase-field mod-eling to bioengineering and provides a mechanistic tool for assessing the service life of bioabsorbable metallic biomedical devices.(c) 2023 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

Automated summary

A phase-field model is developed to simulate the corrosion of Mg alloys in body fluids, capturing both uniform and pitting corrosion. The model takes into account the synergistic effect of aggressive environments and mechanical loading in accelerating corrosion kinetics. It has the potential to assess the service life and optimize the design of Mg-based biomedical devices, promoting the development of Mg alloys as biodegradable implant materials.