XPS Characterization of the Corrosion Films Formed on Nanocrystalline Ni-P Alloys in Sulphuric Acid
✍ Scribed by Splinter, S. J.; Rofagha, R.; McIntyre, N. S.; Erb, U.
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 601 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0142-2421
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✦ Synopsis
X-ray photoelectron spectroscopy (XPS) was used to examine the corrosion films formed on nanocrystalline (nc) and amorphous Ni-P alloys in 0.1 M H,SO,. Neither the nc nor the amorphous alloys were found to exhibit passivity. An enrichment of elemental P compared to Ni was observed at the surface of both materials, suggesting that Ni is preferentially dissolved during anodic polarization. The high volume fraction of grain boundaries and triple junctions on the nc specimens resulted in enhanced dissociative adsorption of oxygen and hydroxyl species from solution. The films formed were, however, non-protective because the defective nc surfaces also facilitated atom dissolution and oxidation of surface P atoms from hypophosphite to soluble phosphate anions. At higher applied potentials, the thick, porous films formed on the nc specimens provided a small kinetic harrier to further dissolution, resulting in slightly lowered anodic current densities compared with amorphous Ni-P.