AN X-RAY PHOTOELECTRON-SPECTROSCOPY STUDY OF THE SURFACE-COMPOSITION OF COXFE80-XSI10B10 METALLIC GLASSES

X-ray photoelectron spectroscopy (XPS) was used to analyze native oxid e films at the surfaces of amorphous ribbons of CoxFe80-xSi10B10 (x = 0, 15, 70, 80). The oxide layer differs in thickness and composition f or the different samples, but no difference in thickness is detected f or the shiny and dull sides of each ribbon, even if different chemical compositions are found. A large surface segregation of silicon is obs erved for the whole set of compositions. Boron has a qualitatively sim ilar but quantitatively less pronounced surface segregation. Iron oxid es are also included in the passive films while cobalt, strongly deple ted at the surface, is present mainly in the non-oxidized form. XPS da ta were compared with the results of corrosion tests obtained by immer sion of the ribbons in acidic solutions of different pH.