Electrochemical Characterization of Amorphous and Crystalline Ni62Nb38 and Ni59.24Nb37.76B3.00 Alloys

Abstract

Nickel-based alloys are widely used in industry due to their remarkable corrosion resistance. Currently, most of these alloys are processed with crystalline structure. However, amorphous metal alloys commonly demonstrate greater corrosion resistance compared to their crystalline counterparts. In this study, the Ni62Nb38, Ni59.24Nb37.76B3.00, and Ni58.1Nb38.9B3.0 (atom percent) alloys with crystalline and amorphous structure were investigated. Traditional X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were used to characterize the alloys. Electrochemical tests were conducted to evaluate the corrosion resistance at different temperatures. Data obtained by electrochemical impedance spectroscopy and polarization curves revealed the superiority of amorphous alloys in relation to crystalline ones, for the same chemical composition. The polarization resistance of the amorphous alloys was up to 20 times greater than that of its crystalline counterparts. Both structures showed a reduction in corrosion resistance with increasing temperature. In amorphous alloys, the presence of boron made the samples more resistant to corrosion at both temperatures. Furthermore, a higher percentage of niobium among the ternary compositions also improved the corrosion properties. In crystalline alloys, the presence of boron resulted in samples that were less resistant to corrosion at a temperature of 25 °C. However, this element provided greater resistance to ternary alloys at a temperature of 45 °C. Using electrochemical techniques, it was possible to demonstrate the superior corrosion resistance of amorphous alloys compared to its crystalline counterparts.