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MA: Magnetismus

MA 11: Magnetische Materialien

MA 11.9: Talk

Tuesday, March 9, 2004, 12:15–12:30, H22

Corrosion behaviour of polymer-bonded Nd-Fe-B-based nanocrystalline magnets — •Mihaela Rada, Anke Kirchner, Annett Gebert, Oliver Gutfleisch, and Ludwig Schultz — IFW Dresden, Helmholtzstr. 20, 01069, Dresden

The corrosion resistance of polymer bonded nanocrystalline NdFeB magnets with Nd-rich, stoichiometric and Fe-rich compositions and that of their main single phases is assessed in aqueous environments. For the evaluation of corrosion properties, gravimetric tests as well as potentiodynamic polarization measurements were performed in different nitrogen-purged electrolytes: 0.1 M sulfuric acid (pH 0.7), 0.5 M phthalate buffer (pH 5) and 0.1 M sodium hydroxide (pH 13). Before and after corrosion testing, the sample surfaces were investigated by means of high-resolution scanning electron microscopy. The single phases show anodic dissolution in strong acidic environment and stable passivation in alkaline solution. In weakly acidic phthalate buffer Nd-rich and Fe phases exhibit limited passive regions, whereas Fe₃B and Nd₂Fe₁₄B do not show stable passivation. Polymer-bonded magnets of different compositions have a significantly improved resistance towards strongly acidic environments as compared to hot pressed magnets. Enrichment in Fe content and additions like Co and Nb improve their corrosion behavior.