XPS Characterization of the Corrosion Films Formed on Nanocrystalline Ni-P Alloys in Sulphuric Acid
1996; Wiley; Volume: 24; Issue: 3 Linguagem: Inglês
10.1002/(sici)1096-9918(199603)24
ISSN1096-9918
AutoresS.J. Splinter, R. Rofagha, N. S. McIntyre, U. Erb,
Tópico(s)Corrosion Behavior and Inhibition
ResumoX-ray photoelectron spectroscopy (XPS) was used to examine the corrosion films formed on nanocrystalline (nc) and amorphous Ni–P alloys in 0.1 M H2SO4. 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 speciesfrom solution. The films formed were, however, non-protective because the defective nc surfaces also facilitatedatom dissolution and oxidation of surface P atoms from hypophosphite to soluble phosphate anions. At higherapplied potentials, the thick, porous films formed on the nc specimens provided a small kinetic barrier to further dissolution, resulting in slightly lowered anodic current densities compared with amorphous Ni–P.
Referência(s)