XPS analysis of passive films on the amorphous alloy Fe70Cr10P13C7: Effect of the applied potential

Passive films formed in 1N HCI at different potentials on mechanically polished samples of the alloy Fe70Cr10P13C7 were studied by XPS surface analysis. The thickness of the films increases with the applied potential; at 0.4 V/SCE (saturated calomel electrode) a discontinuity is observed. The passive films are enriched in chromium oxyhydroxide; phosphates are incorporated in notable amounts. The substrate underneath the film is enriched in phosphorus. The outstanding corrosion resistance of this alloy may thus be attributed to this enrichment of phosphorus underneath the film, reducing to a great extent the ionic conductivity of the interface, and to the incorporation of phosphates in the passive film.