Evaluating corrosion resistances of Fe-based amorphous alloys by YCr/Mo values

Abstract

In this paper, the synthetic effect of Cr, Mo and Y on corrosion resistance was explored, and the YCr/Mo value was employed to evaluate the corrosion resistance. The composition of amorphous alloy was designed by mixing the Fe41Co7Cr15Mo14C15B6Y2 (BMG1) with good glass forming ability (GFA) and Fe50Cr22B23Ni5.4 with a high corrosion resistance at 9:1 ratio. At the same time, the contents of Y, Mo and Cr were fine-tuned. The electrochemical tests demonstrated that the passivation current density decreased with the increase of the YCr/Mo value. The passivation current density of Fe-based amorphous alloy was reduced by about half an order of magnitude. The fitting result showed that the logarithm of passivation current density (I) and the YCr/Mo value (X) were logarithmic relationship, and the fitting equation was I=–5.649+4.904×1015e−17.52x. The X-ray photoelectron spectroscopy (XPS) results showed that the YCr/Mo value played a key role in stability of passive films. When the YCr/Mo value was low, the Cr6+ ion, Mo6+ ion were enriched in the initial stage of passivation process, then leading to the increase passivation current density. However, when the YCr/Mo value was high, the low-valence Fe2+, Cr3+, and Mo4+ ion were enriched more easily, which result in small passivation current densities and more stable passive films.