Study on corrosion property of fluoride treated biodegradable AZ31 magnesium alloy

In order to improve the corrosion resistance of Mg alloys as degradable implant material, fluorine conversion coatings were synthesized on AZ31 magnesium alloy by immersion in hydrofluoric acid (BF) for different time. Potentiodynamic electrochemical technique and hydrogen evolution testing were employed to investigate the corrosion behavior of the coated alloys in Hank's solution. It is indicated that the fluoride conversion coating, which is compact and composed of MgF2, can significantly decrease the degradation rate of Mg alloy AZ31 in Hank's solution. The most improved corrosion protection was achieved by immersion for 10 days. The corrosion current density was 40 times lower than that of the substrate and. the hydrogen evolution rate of the coated sample was only one-fiftieth of the substrate.