Corrosion behavior of bulk amorphous Zr₅₅Al₁₀Cu ₃₀Ni_5-xPd_x alloys

Bulk amorphous Zr₅₅Al₁₀Cu₃₀Ni _5-xPd_x (x=0, 5at.%) alloys were produced by copper mould casting. The microstructure of samples was characterized by X-ray diffraction (XRD). The corrosion resistance of the bulk amorphous alloys was studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The Pd-free alloy showed an active-passive transition by anodic polarization in 3.5% NaCl solution, it was spontaneously passive and had a wide passive region with significantly low passive current density. The 5% Pd amorphous alloy shows a single active state even with a limited passive region. X-ray photoelectron spectroscopy (XPS) analysis revealed that the spontaneous passive films formed on the alloys after immersion in 0.6 M NaCl solution for 72 h were composed of the oxidation of Zr, Al and Cu element. The Pd-free and 5% Pd alloys show excellent corrosion properties in 1 M NaOH solution.