Superior corrosion resistance of high-temperature annealing Cr–Co–Mo–Nb–B metallic glass in sodium chloride solution

Abstract

In this study, it was investigated the effects of different annealing temperature on the corrosion behavior of Cr₂₆Co₂₆Mo₂₆Nb₇B₁₅ high-temperature metallic glass in a 3.5 wt% NaCl solution. The results revealed that annealing below the glass transition temperature significantly enhanced the corrosion resistance, with the optimal performance achieved at 1008 K. At this temperature, the self-corrosion current density and potential reached 7.19 × 10⁻⁹ A·cm⁻² and 0.14 V, respectively, while the passive region expanded to 1.298 V, demonstrating the superior stability in the 3.5 wt% NaCl solution. The superior corrosion resistance can be attributed to the increased contents of Cr³⁺, Mo⁴⁺, and Mo⁶⁺, as well as the synergistic effect between Cr and Mo. Annealing below T_g also induces the structural relaxation of the Cr₂₆Co₂₆Mo₂₆Nb₇B₁₅ metallic glass. This process annihilates the free volume within the alloy and increases its hardness, leading to a lower energy state compared to the as-quenched state, which also contributes to the corrosion resistance.