Corrosion behaviors of thermally grown oxide films on Fe-based bulk metallic glasses

Oxide films formed on the surfaces of Fe-based bulk metallic glasses in the temperature range between 373 K and 573 K were characterized and their effects on the corrosion behaviors were investigated by microstructural and electrochemical analysis. The oxide film formed at 573 K is iron-rich oxide and it exhibits an n-type semiconductor at a higher potential than 0.35 V and a p-type semiconductor at a lower potential than 0.35 V. Capacitance measurements show that the donor density decreases with the increase in oxidation temperature, while the thickness of the space charge layer increases with the oxidation temperature rising. The result of immersion tests shows that the mass loss rate increases with the oxidation temperature rising. Therefore, the correlation between microstructure and corrosion resistance needs to be proposed because the corrosion resistance is deteriorated with the development of the oxide films.