Corrosion Behavior of Ni-Nb Eutectic Glassy Composition in Aqueous Solutions of NaOH, HCl, and NaCl

EIS and cyclic polarization curves in HCl 1 M, NaOH 1 M and NaCl 0.5 M were used to analyze the corrosion mechanism in eutectic Ni-Nb metallic glass composition. Glassy ribbons were synthesized by melt spinning technique by varying the wheel spinning speed with 12 and 25 m/s to produce ribbons of two thicknesses. The vitrification of the alloy was confirmed by XRD, which showed a diffuse characteristic peak of glassy structures. The analyses showed that at pH 0 and 7, the glassy alloy is immune to pitting in its passive layer. Furthermore, it shows regeneration of the damaged areas, repairing those where nickel is lost with niobium oxide. In alkaline media, the passive layer is unstable due to the formation of oxides, increasing the corrosion rate by 0.02 mpy compared to chloride media. When exposed to chloride media and sodium hydroxide, SEM analysis showed no significant damage to the alloy. Finally, XPS was used to analyze the species formed on the surface. Several Ni and Nb oxides were found along different pHs; those species allowed localized corrosion protection, regenerating the damaged zones and corroborating the passive layer’s self-healing effect. This effect and the lack of crystalline defects provide high anticorrosion protection of the material.