X-ray Photoelectron Spectroscopic Study on the Anodic Passivity of Sputter-deposited W-Nb Alloys in 12 M HCl Solution

Abstract

The effect of a simultaneous additions of  tungsten and niobium on the anodic passivity of the surface films of the sputter-deposited amorphous/nanocrystalline W-xNb alloys was studied using corrosion tests, electrochemical measurements and X-ray photoelectron spectroscopic (XPS) analyses. The formation of spontaneous passive film on the alloys, which is composed of double oxyhydroxides of W^ox and Nb⁵⁺ ions, is responsible for their higher corrosion resistance than those of the alloy-constituting elements in 12 M HCl solution open to air at 30°C. The quantitative surface analysis by XPS clarifies that the improved anodic passivity of the alloys than those of alloy-constituting elements is based on the formation of new double oxyhydroxide anodic films composed of W⁶⁺ and Nb⁵⁺ ions. These anodic passive films have higher protectiveness and stability than those of the anodic passive oxyhydroxide films of alloy-constituting elements, that is, oxyhydroxides of hexavalent tungsten and pentavalent niobium after potentiostatic polarization for 1 h in 12 M HCl at 30°C.

Keywords: W-Nb alloys; Sputter deposition; Polarization curve; Passivity; Surface analysis.

© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.

doi:10.3329/jsr.v3i3.7207               J. Sci. Res. 3 (3), 467-480 (2011)