Performance of pulsed constant current silicate-based PEO coating on pure magnesium in simulated body fluid

In vitro degradation behaviour of a pulsed constant current silicate-based PEO coating on pure magnesium was studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation techniques. The PEO coating increased the polarisation resistance (Rp) of magnesium by an order of magnitude and reduced the corrosion current (icorr) by 65%. EIS modelling indicated that the inner compact layer resistance of the PEO coating was critical for the overall degradation resistance of the material. However, the breakdown potential from potentiodynamic polarisation curves and the post-degradation analysis suggested that the porous outer layer of the PEO coating played an important role in the stability of the inner compact layer.