X-ray photoelectron spectroscopy study of the surface composition of CoxFe80-xB10Si10 metallic glasses

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