Do phosphate ions affect the biodegradation rate of fluoride-treated Mg?

ALONSO C; DEL VALLE JA; GAMERO, M; FERNÁNDEZ LORENZO DE MELE, M

MATERIALS LETTERS

ELSEVIER SCIENCE BV

Año: 2012 vol. 68 p. 149 - 152

0167-577X

Previous studies have shown that pure Mg that is reinforced by powder metallurgy (Mg(PM)) is a promising biodegradable material, because it circumvents the drawbacks of the toxic components of Mg alloy implants. However, its degradation rate is high, which can be reduced with fluoride coatings (Mg(PM)F). This protective effect is temporary, because chloride induces further biodegradation of Mg(PM) in biological media. The aim of this report was to examine the effects of phosphates on Mg(PM)F in chloride-containing medium. By surface analysis of Mg(PM)F, the aggressive activity of chlorides induced a rapid decrease in F content of the layer. However, by electrochemical impedance spectroscopy and EDX, the surface attack was hindered in the presence of phosphates that precipitated onto the regions where localized attack occurred and formed a more protective P-containing layer. Our results highlight the robust activity of phosphates, which act synergistically with fluorides, controlling the degradation of F-coating in biological media and prolonging the service period of temporary Mg(PM)F implants.