Corrosion mechanisms of Zr-based bulk metallic glass in NaF and NaCl solutions

Abstract

So far, some investigations related to the corrosion mechanism of Zr-based metallic glasses in solutions containing Cl− have been developed. However, few attentions have been paid to the situation in F−-containing solution. This paper describes the corrosion behaviours of Zr52Al10Ni6Cu32 bulk metallic glass (BMG) in NaF and NaCl aqueous solutions. The corrosion mechanism of Zr-based BMG in F--containing solution was proposed for the first time. It was found that in NaCl solutions, Zr-based BMG samples underwent typical pitting corrosion. Selective dissolution of Zr, Al and enrichment of Cu were observed in corrosion pits. However, corrosion occurred in the form of general breakdown of passive film in NaF solutions. Such difference is interpreted in terms of the binding ability of anions to surrounding molecules, i.e., Cl− with loose surrounding water passes through the passive film to cause pitting; F− with a tight surrounding molecules layer absorbs on passive film then coordinates with cations from matrix.