Corrosion protection of biodegradable magnesium implants using anodization

Magnesium (Mg) and its alloys are emerging as a possible biodegradable implant material. However, Mg implants may degrade too quickly in the body, before the natural healing process is complete. In this work, anodization was investigated to slow down the initial corrosion of Mg in a simulated body corrosive environment. Pure Mg and AZ91D alloy were anodized and their corrosion resistance was compared in terms of anodization behavior and parameters such as applied voltage and current with different anodization time. Electrochemical impedance spectroscopy, DC polarization, and immersion testing were used to evaluate the corrosion resistance of Mg samples and further optimize anodization parameters. The results showed that anodization increased the corrosion resistance of both pure Mg and AZ91D samples. Further characterization showed the anodized layers on both pure Mg and AZ91D consisted of Mg, O and Si, in the mixture of MgO and Mg2SiO4.