2012 年 1 巻 6 号 p. 293-297
Magnesium (Mg) and it alloys are highly corrosive due to their low standard electrode potential (SEP). The conventional methods to improve corrosion resistance of Mg alloys are anodic oxide film formation and chemical conversion treatment. However, these methods are expensive and also make it hard to recycle the Mg products with these treatments. In this study, unique oxide layer formed by radical reaction between pure Mg surface and radical species generated under X-ray irradiation was investigated. Pure Mg surface was modified by X-ray irradiation under atmospheric condition. XPS analysis indicated MgO layer was formed at the surface of X-ray irradiated pure Mg specimen. Cross-sectional observation by TEM showed the MgO layer was dense compared to the natural oxidation coating films. The thickness of surface modification layer by X-ray irradiation was increased with the increase of irradiation time. After salt water immersion test, X-ray irradiated pure Mg for 24 hours showed about four times corrosion resistance of the as-polished original pure Mg. These results suggest that dense MgO layer formed by X-ray irradiation on pure Mg surface were functioning as a protective film.