Effect of surface roughness on the in vitro degradation behaviour of a biodegradable magnesium-based alloy

In this study, the in vitro degradation behaviour of AZ91 magnesium alloy with two different surface finishes was investigated using electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF). The polarisation resistance (Rp) of the rough surface alloy immersed in SBF for 3 h was ~30% lower as compared to that of the smooth surface alloy. After 12 h immersion in SBF, the Rp values for both the surface finishes decreased and were also similar. However, localised degradation occurred sooner, and to a noticeably higher severity in the rough surface alloy as compared to the smooth surface alloy.