Effect of atomic mobility on the electrochemical properties of a Zr₅₈Nb₃Cu₁₆Ni₁₃Al₁₀ bulk metallic glass

The corrosion behaviour of bulk metallic glasses is greatly related to their microstructures. The microstructures in bulk metallic glasses of the same chemical composition are represented to a certain extent by their atomic mobility. Evolution of the microstructure and mechanical properties of Zr₅₈Nb₃Cu₁₆Ni₁₃Al₁₀ bulk metallic glass after annealing were studied with X-ray diffraction, dynamic mechanical analysis and Vickers hardness tests. Polarization curve, open circuit potential, electrochemical impedance spectroscopy and Mott-Schottky analysis were performed to investigate the effect of atomic mobility on the corrosion behaviour in 1 mol/L de-aerated H₂SO₄ at 333 K. Dynamic mechanical analysis indicated that the atomic mobility of Zr₅₈Nb₃Cu₁₆Ni₁₃Al₁₀ bulk metallic glass was reduced by structural relaxation and crystallization. All electrochemical measurements showed that the passivation ability decreased and the corrosion resistance of Zr₅₈Nb₃Cu₁₆Ni₁₃Al₁₀ bulk metallic glass deteriorated as the annealing temperature increased. Mott-Schottky analysis revealed that the defect concentration in the passive films increased and the flat-band potential shifted to a negative potential with a decrease in the atomic mobility. X-ray photoelectron spectroscopy results proved that the main chemical compositions of the passive films were ZrO₂, Al₂O₃ and Nb₂O₅. The formation of a passive film was suppressed because the atomic mobility of strong passivating elements (Zr, Al and Nb) decreased. In addition, the precipitation of crystals (Zr₂Cu and Cu₁₀Zr₇) accelerated the corrosion of the bulk metallic glass in H₂SO₄.