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MM: Fachverband Metall- und Materialphysik

MM 47: Liquid and Amorphous Metals III

MM 47.7: Vortrag

Freitag, 27. März 2009, 11:45–12:00, IFW A

Corrosion behaviour of the (Fe_44.3Cr₅Co₅Mo_12.8Mn_11.2C_15.8 B_5.9)_98.5Y_1.5 bulk metallic glass and its crystalline counterpart — •Petre Gostin, Uwe Siegel, Annett Gebert, Uta Kühn, Jürgen Eckert, and Ludwig Schultz — IFW, Dresden, Germany

The corrosion behaviour of the bulk glassy (Fe_44.3Cr₅Co₅Mo_12.8Mn_11.2
C_15.8B_5.9)_98.5Y_1.5 alloy and its crystalline counterpart was assessed by employing anodic polarization tests in combination with microscopy techniques: transmission and scanning electron microscopy and atomic force microscopy. The crystalline counterpart is composed mainly of simple and complex carbides surrounded by an iron based solid solution phase which is preferentially dissoluted in most of the electrolytes used in the tests. The passivation ability was studied in electrolytes with various pH values ranging from 0 to 14. When compared with the bulk glassy alloy, the crystalline counterpart is less noble in all the electrolytes, but exhibits no significant difference in the anodic polarization behaviour. Both of them exhibit low corrosion current densities in the whole pH value range (<3 µA/cm²). The passivation ability is very poor in strongly acidic solutions and improves with increasing pH, being the best at pH 11. Passive films on the glassy sample were characterized by Auger electron spectroscopy. They are composed mainly of Fe and Cr oxides. Passivity greatly depends on the electrolyte composition: sulphates, as well as chlorides worsen the passive film protective character. Still, at room temperature, chloride concentrations up to 1 M do not bring about pitting. The influence of the alloy composition on passivity is discussed.