Corrosion studies on amorphous and crystalline Zr₆₇Ni₃₃

Abstract

The room temperature corrosion behaviour of an amorphous alloy, Zr₆₇Ni₃₃, known to undergo polymorphic crystallization, in 1 N HCl, 1 N H₂SO₄ and 1 N HNO₃ was compared with that of a crystalline alloy of the same composition. Weight loss studies indicated that the corrosion resistance of the amorphous alloy was greater than that of the crystalline alloy and that HCl was the most corrosive of the three media used. Concentration depth profiles of the elements constituting the film, obtained by AES, showed that in all the three media an enrichment of nickel by approximately a factor of two at the oxide film-alloy interface as well as a larger oxygen uptake occurred in crystalline specimens as compared with the amorphous specimens. The Auger profile also showed that for both the amorphous and the crystalline samples, the oxide film formed in HCl was the thickest, followed by those in H₂SO₄ and HNO₃. Analysis of Zr 3d_5/2 and O 1s XPS peaks revealed that the surface oxide film formed in all the media consisted of zirconium oxide (ZrO₂) as well as a hydroxide of zirconium (possibly Zr(OH)₄).