XPS STUDIES ON PASSIVE FILMS ON AMORPHOUS FE-CR-(B,P)-C ALLOYS

Passive films on amorphous Fe-10Cr-13B-7C and Fe-10Cr-13P-7C have been studied with X-ray photo-electron spectroscopy (XPS) after passivatio n in 1N H2SO4 containing Cl-. The most notable feature of the passive films of the amorphous alloys compared to that of a crystalline Fe-17C r steel is the high amount of oxidized metalloids present in the film. On the surface of the amorphous Fe-1OCr13B-7C and the crystalline Fe- 17Cr significant amounts of sulfate were found, whereas on the surface of the amorphous Fe-10Cr-13P-7C alloy the amount of electrolyte anion s was almost non-detectable. The anion repelling effect of the passive film on the P-containing alloy is most probably due to the presence o f oxidized phosphorus as PO43- in the passive film. As a consequence a coulombic barrier against anion adsorption is formed, which leads to a high localized corrosion resistance of the P-containing alloy.