Cathodic protection: A new strategy to enable the formation of nanostructured polypyrrole on magnesium

Cathodic protection, a conventional technique of protecting metal from corrosion, was used to enable the formation of polypyrrole (PPy) film on biodegradable metal magnesium (Mg). The formation procedure was as follows: first, Mg corrosion was suppressed by applying a negative potential to the Mg cathode; second, oxidant nitrosyl ion (NO+) was generated on Mg surface through a redox reaction that obtained electron from Mg; third, pyrrole was oxidized to polypyrrole on Mg by NO+. It was interesting to observe that the formed PPy exhibited porous nanostructured morphology. Subsequent corrosion tests showed that the PPy coating could slow down the Mg corrosion in physiological saline, but could not stop corrosion completely, which was especially useful for a coating material of biodegradable metal implants.