Tracer study of oxygen and hydrogen uptake by Mg alloys in air with water vapor

The oxidation of pure Mg, Mg–3Al–1Zn (AZ31B), and Mg–1Zn–0.25Zr–<0.5Nd (ZE10A) was studied at 85°C in humid air using sequential exposures with H218O and D216O for water vapor. Incorporation of 18O in the hydroxide/oxide films indicated that oxygen from water vapor participated in the reaction. Penetration of hydrogen into the underlying metal was observed, particularly for the Zr- and Nd-containing ZE10A. Isotopic tracer profiles suggested a complex mixed inward/outward film growth mechanism.