Improved corrosion resistance and biocompatibility of magnesium implants by cathode-deposited polypyrrole/dicalcium phosphate dihydrate composite coating

As a new-generation of concerned biomedical metal implants, magnesium (Mg) alloy has the degradability, biocompatibility and mechanical properties close to human bones that inert metals do not have. However, the side effects caused by rapid degradation become the biggest obstacle restricting its practical application. Here, we report that the preparation of polypyrrole/calcium phosphate (PPy/CaP) composite coating on Mg alloy by the application of the cathode deposition twice in a row, which delayed the corrosion of Mg alloy and reduced its corrosion current density, the biocompatibility was also greatly improved. This method is simple to operate, and could get a tightly bonded PPy coating on active metals without passivation treatments. It also avoids the substrate exposure due to the high solubility of the single electrodeposited calcium phosphate coating, and finds the future direction for application of electrodeposited modified Mg alloy.