Evaluation of corrosion resistance of biocompatible coatings on magnesium

The work deals with the study of innovative biocompatible coatings for magnesium resorbable osteosynthesis devices. Conversion layers based on magneium fuoride and "diamond like carbon" coating (DLC) obtained by chemical vapor deposition were considered in order to reduce the corrosion rate of magnesium to levels compatible with the time needed for fracture healing. DLC coating was applied on both pure magnesium and on magnesium after conversion treatment in hydrofluoric acid. Weight loss tests and potentiodynamic polarization tests in aerated Hank's solution at room temperature were performed. The corrosion rate was about 100mg/cm2day for the commercially pure magnesium (99.9%) in the first 24 hours of exposure. Both the coatings reduced the short-term corrosion rate but the protective layers did not grant long-term stability and corrosion rate rapidly increases approaching the values of uncoated magnesium.