Assessing the corrosion of biodegradable magnesium implants: A critical review of current methodologies and their limitations

Magnesium (Mg) and its alloys have been intensively studied as biodegradable implant materials, where their mechanical properties make them attractive candidates for orthopaedic applications. There are several commonly used in vitro tests, from simple mass loss experiments to more complex electrochemical methods, which provide information on the biocorrosion rates and mechanisms. The various methods each have their own unique benefits and limitations. Inappropriate test setup or interpretation of in vitro results creates the potential for flawed justification of subsequent in vivo experiments. It is therefore crucial to fully understand the correct usages of each experiment and the factors that need to be considered before drawing conclusions. This paper aims to elucidate the main benefits and limitations for each of the major in vitro methodologies that are used in examining the biodegradation behaviour of Mg and its alloys.