CORROSION BEHAVIOR OF FE80-XCOXB10SI10 METALLIC GLASSES IN SULFATE AND CHLORIDE MEDIA

The corrosion behaviour of a series of glassy alloys, Fe80-xCox-B10Si1 0 (x = 0, 15, 30, 55, 70, 80), well known for their magnetic propertie s. has been investigated in sulphate- and chloride-containing solution s of different pH, employing weight loss measurements. In order to poi nt out preferential dissolution reactions of metallic glasses constitu ent elements, analyses of the solutions were performed after corrosion tests by means of plasma source mass spectrometry and optical emissio n spectroscopy. A higher aggressivity of the sulphate containing solut ions has been observed. The amorphous alloys exhibit an increased corr osion resistance with the increase of cobalt content. Increasing the p H of the aggressive media from 1.5 to 5.6 a decrease of two orders of magnitude in the corrosion rates has been observed. The corrosion prod ucts have been investigated by means of X-ray diffraction and scanning electron microscopy. Hydrated iron oxide Fe2O3. H2O was the major con stituent of the film formed on iron-rich amorphous alloys immersed in sulphate-containing media.