Influence of thermomechanical post-treatment on the corrosion behavior of Ni57Nb33Zr5Co5 bulk metallic glass

Improving the Corrosion Resistance of NiNb-Based Bulk Metallic Glass through the Hot Compression

“…Another point in the polarization curves is the existence of a passivation plateau for all the samples with a current density in the range of 3.8-4.1 µA•cm −2 . It is seen that the passive flms exhibit a stable condition, while the water oxidation occurs near +1.5 V Ag/ AgCl [8], leading to rise of current density under the polarization. It is worth noting that the criterion for selecting an alloy as bipolar plates is to have i corr less than 16 µA•cm −2 [26].…”

“…For treated Ni 55 Nb 45 , the i corr and E corr values are 0.58 µA•cm −2 and −01 V SCE , respectively. Tis outcome implies that the crystallization induces the elemental partitioning and increases the anomalous chemical interfaces, leading to deterioration of corrosion resistance in the alloy [8]. On the other hand, the treated Ni 55 Nb 35 Co 5 Zr 5 alloy shows excellent corrosion behavior with the i corr and E corr values of 0.05 µA•cm −2 and 0.143 V SCE ; however, this sample also includes the crystalline phases in its microstructure, as seen in Figure 1.…”

“…To measure the electrochemical parameters, an Origa-Stat200 potentiostat was used along with a saturated Ag/ AgCl electrode as reference and a platinum mesh as a counter-electrode. To simulate the environment of proton exchange membrane fuel cells, 2 ppm F + 1 M H 2 SO 4 at 70 °C were prepared [8,25]. Prior to any measurement, the working electrode was left at open circuit potential for 2 hours.…”

“…A wide range of properties from corrosion resistance to fexural strength is needed for considering a material as a bipolar plate [4][5][6]. Among a broad spectrum of alloy compositions in the glassy systems, Ni-based BMGs are promising alloys with excellent corrosion resistance, which can be employed as bipolar plates in the proton exchange membrane fuel cells [7,8]. Several processes such as annealing, microalloying, and thermomechanical treatments have been carried out to improve the corrosion resistance of Ni-based BMGs as much as possible.…”

“…Zhao et al [20] also reported that the corrosion behavior of the deformed ZrCuNiAl MG after heat treatment is much better than that of the deformed MG prior to the heat treatment. Figueira et al [8] demonstrated that the thermomechanical posttreatment was an efcient method for improving the corrosion resistance of NiNb-based BMGs. It was also found that the severe surface deformation led to an alteration of free volume and enhancement of bio-corrosion resistance in the BMGs [21].…”