Corrosion Behavior of a Monolithic Zr-Cu-Al-Ag Bulk Metallic Glass and a Zr-Cu-Al-Ag Bulk Metallic Glass Matrix Composite in Sodium Chloride Medium

The corrosion mechanism and corrosion behavior of a monolithic Zr-based (Zr48Cu36Al8Ag8)Si0.75 bulk metallic glass (BMG) and a Zr-based (Zr44Cu36Al8Ag8Ta4)Si0.75 BMG matrix composite (BMGMC) in 3.5 wt.% NaCl solution were investigated. Potentiodynamic polarization tests were conducted to evaluate the corrosion and passive behavior of BMGs. Both monolithic BMG and BMGMC exhibited distinct pitting corrosion in sodium chloride solution. The monolithic BMG exhibited a higher value of pitting overpotential, ηpit, and a wider passive region, when compared to that of BMGMC, indicating that the monolithic BMG has a better pitting resistance than the BMGMC. The worse corrosion resistance of BMGMC can be attributed to the weak passive film of the interface area between the precipitates and the glassy matrix, where it can be more easily broken through by halide ions, Cl−, preferentially. Furthermore, galvanic corrosion can occur due to the potential difference between Ta precipitates and the matrix of BMGMC, leading to an even more severe corrosion of the BMGMC.