FIB-TEM Study of Magnesium Corrosion Products after 14 Days in the Murine Artery

After a decade of intensive research on magnesium biodegradation, the composition and structure of corrosion products formed during in vivo corrosion are still not precisely known. Focused ion beam (FIB) micromilling and transmission electron microscopy (TEM) were used to elucidate the nanostructure and crystallography of the corrosion products that form at or near the interface between the corrosion products and metallic magnesium. This study built upon previously reported scanning electron microscopy, infrared spectroscopy, and energy dispersive X-ray spectroscopy data. These prior results revealed a duplex corrosion layer comprising a calcium- and phosphorus-containing outer product (near the tissue interface) and a magnesium- and oxygen-containing inner product (near the metallic interface). A specimen that had resided in the murine arterial wall for 14 days was selected for FIB-TEM analysis. Highly oriented, nanocrystalline magnesium oxide was identified near the metallic magnesium, apparently without the co-occurrence of magnesium hydroxide or carbonates. The calcium- and phosphorus-containing surface layer was also examined, and shown to be nearly amorphous.