Studies on the corrosion of two multicomponent iron base metallic glasses in potassium sulphate solution

Abstract

Corrosion studies were carried out on two multicomponent iron based metallic glasses, Fe₈₁B_13.5Si_3.5C₂ (METGLAS 2605SC) and Fe₈₇Co₁₈B₁₄Si (METGLAS 2605CO), in a 0.5 M potassium sulphate solution of pH 4.0. Weight loss measurements indicated comparable corrosion rates for the two alloys. Potentiostatic polarization studies showed nearly the same cathodic currents for these alloys during cathodic polarization. During anodic polarization, lower currents were obtained for the 2605CO alloy as compared to the 2605SC alloy. Neither of the alloys exhibited passivity during anodic polarization. Auger Electron Spectroscopy and X-ray Photo-electron Spectroscopy studies showed that FeOOH was the major constituent of the film formed on the 2605SC alloy and that in the case of the 2605CO alloy, a mixture of FeOOH, Co(OH)₂ and CoO was present in the corrosion film. An enrichment of C, B, and Si occurred in the film formed on the first alloy while that formed on the latter was enriched in Co. These two amorphous alloys were found to be more resistant to corrosion in potassium sulphate solution as compared to the binary Fe₈₀B₂₀ glass. Enrichment of the surface film in the constituent metalloid species in the case of the 2605SC glass and Co enrichment of this film in the case of the 2605CO glass appears to contribute to this enhanced corrosion resistance.