Abstract
The effect of Si and Ge on the passivation properties of Fe 75Al 25 intermetallic compound has been evaluated in 0.25 M H 2SO 4 solution by means of potentiodynamic polarization, potentiostatic transients and electrochemical impedance spectroscopy (EIS) techniques. Fe 75Al 25 and Fe 70Al 25M 5 (M = Si, Ge) intermetallic compounds were prepared by arc melting the stoichiometric amounts of pure elements in argon atmosphere. All the investigated iron aluminides exhibit a single-phase microstructure. Electrochemical studies reveal an improvement in the protective properties of passive films formed on Fe 70Al 25Si 5 and Fe 70Al 25Ge 5 intermetallics as compared to Fe 75Al 25. XPS analysis of the surface layers anodically grown on ternary iron aluminides indicate that the passive films are composed of Al 2O 3, Fe 2O 3 and SiO 2 or GeO 2, thus explaining the better passivation characteristics of Fe 70Al 25Si 5 and Fe 70Al 25Ge 5 intermetallics with respect to Fe 75Al 25.
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