Effect of microstructure on corrosion behaviours of a Ni-based metallic glass

Abstract

Electrochemical corrosion behaviours of as-spun, as-cast, and relaxed Ni55Nb20Ti10Zr8Co7 metallic glasses were investigated in 3 mass% NaCl and 1 N H2SO4 solutions in order to study the effect of different amorphous microstructure. Static immersion tests indicate that the as-spun ribbon possesses the most active state in the NaCl solution at its open circuit potential, followed by the as-cast rod, the relaxed ribbon, and the relaxed rod. While in the H2SO4 solution, the rod samples are more stable than the ribbons, and the relaxed samples exhibit higher stability than the as-quenched samples. The polarization tests revealed slightly higher passive current density (ipass) for the ribbons than those of the rods in both electrolytes, although no significant differences in ipass were found between the relaxed and the as-quenched specimens. It is concluded that electrochemical corrosion behaviours of metallic glasses are related to the amorphous structure, and a decrease in free volume generally favors corrosion resistance.