Corrosion of porous Mg and Fe scaffolds: a review of mechanical and biocompatibility responses

Absorbable metals have been proposed as potential materials for hard tissue scaffolding to offer both high mechanical support and bioabsorbability. Over the past 5 years, many works sought evidence of the interesting mechanical property which mimics to that of human bone with tailored corrosion behaviour. The emerging additive manufacturing (AM) technology helps to optimise the design and production of topological porous absorbable metals suited for bone scaffolds. Since the studies on the porous absorbable metals are on the rise, we provide a current state-of-the-art of corrosion performances for porous Mg-based and Fe-based scaffolds including recent developments and the remaining challenges. A detailed discussion on the impacts of advanced AM and recently developed dynamic-flow corrosion on their in vitro corrosion, mechanical strengths and biocompatibility are also provided. This review also analyses the suitability of both metals to be used for bone substitute materials.