Corrosion mechanisms of Zr-based bulk metallic glasses in NaBr solution

In this paper, the corrosion mechanisms of Zr55Cu35Al10 and Zr56Co28Al16 bulk metallic glasses (BMGs) in 3.5 wt.% NaBr solution was systematically investigated by the kinetic potential polarization and electrochemical impedance spectroscopy. Both Zr55Cu35Al10 and Zr56Co28Al16 BMGs were subjected to pitting damage during the polarization process in NaBr solution due to the presence of Br- ions. However, Zr56Co28Al16 BMG exhibits better corrosion resistance compared to Zr55Cu35Al10 BMG. Zr55Cu35Al10 BMG experiences selective dissolution of alloying elements under the attack of Br-, and Cu element was enriched in the corrosion pit. The surface of Zr56Co28Al16 BMG shows a more uniform distribution of elements after corrosion. Simultaneously, the substitution of Cu by Co changes the composition of the passive films and increases the relative content of ZrO2, which is a principal factor contributing to the enhanced stability of Zr56Co28Al16 BMG's passive film.