A mechanistic in vitro study of the microgalvanic degradation of secondary phase particles in magnesium alloys

The aim of this work was to understand the effect of microgalvanic degradation on secondary phase particles in magnesium alloys under in vitro condition. Pure magnesium and Mg17 Al12 (β-phase) were galvanically coupled in simulated body fluid and the degradation behavior was studied using electrochemical impedance spectroscopy. The galvanic coupling produced a phosphate/carbonate layer on the β-phase, which initially increased the degradation resistance. However, the deposited phosphate/carbonate layer rapidly degraded once the galvanic coupling was removed, and β-phase exhibited similar degradation resistance to that of pure magnesium. A phenomenological model has been presented, demonstrating the galvanic coupling effect.