Study On The Corrosion Behavior Of Mg As A Degradable Hard Tissue Implant Material

Magnesium has potential to be biomaterial because of its low density, high specific strength and good biological compatibility. Mg has low corrosion resistance, which can be an advantage for Mg to be a degradable hard tissue implant material. It is the target to control the corrosion rate to match the concrescence rate of bone.The main ions in SBF affect the corrosion behavior of Mg. Those effects were investigated to explain the corrosion mechanism of Mg in SBF. As a result, a reasonable project for controlling the corrosion rate was brought forth. In addition, the choice of SBF at present depends mostly on reproducing the bioactivity with the corrosion problem ignored, so the other aim of this paper is to attract the attention to this aspect.Before the vivo tests, the biomaterial usually needs to be tested in SBF. In this paper, the influence of SBF ions on corrosion of Mg in SBF was investigated by electrochemical method in the solution with different concentration of ions, and the corrosion mechanisms affected by different ions were discussed. When Mg was corroding in SBF, substance like apatite was produced, which combined with Mg(OH)₂ to form a mixed film in surface. The generation and break of this film greatly influenced the corrosion behavior. This paper studied the effects of four ions involving Cl^-,HCO₃^-,HPO₄^2- and Ca²⁺. Cl^- accelerates the corrosion by breaking the film; HCO₃^- has double influences of both protection and break on the corrosion of Mg in SBF; HPO₄^2- and Ca²⁺ take part in producing the film to affect the corrosion.This paper also investigated the corrosion behavior of Mg treated by micro-arc oxidation. The result is shown to be different from pure Mg that its corrosion rate was about two orders lower than pure Mg's.