Dissolution and passivation of nickel. An X-ray photoelectron spectroscopic study

Abstract

The presence and nature of surface species formed on a nickel electrode after polarisation in 0.5 mol dm^–3 sulphuric acid and 0.5 mol dm^–3 sulphuric acid + 0.005 mol dm^–3 nickel sulphate has been investigated by X-ray photoelectron spectroscopy. The film produced in the active, prepassive, passive and transpassive regions was studied. Nine different species were detected including two sulphur species. In all cases the electrode was transferred to the spectrometer under nitrogen to minimise air oxidation of the metal or film. The binding energies and intensities of the photoelectron peaks were analysed and showed the presence of NiO and Ni(OH)₂. The thickness of the film in the passive and transpassive regions was calculated, assuming a continuous layer, as 10–20 Å.