Abstract
The structure and composition of passive films electrochemically formed on Ni‐Cr alloys in 1 M NaOH and 0.5 M has been studied with x‐ray photoelectron spectroscopy. The passivation potential was varied within the passive range up to the transpassive range and the time of passivation from 10 ms to 1000 s. With angular‐resolved x‐ray photoelectron spectroscopy, the passive film was found to have a two‐layer structure with an inner oxide part formed directly at the metal surface and an outer hydroxide part in contact with the electrolyte. The metal surface underneath is enriched in Ni compared to the metal bulk composition. Except for potentials approaching the transpassive range, the hydroxide layer forms the dominant part of the passive film. Above 0.3 V in NaOH and 1.2 V in , Cr(VI) ions are found within the hydroxide layer. The maximum thickness of the passive layer is about 6 nm in NaOH and 3.5 nm in . The growth and the pronounced changes of the composition of the passive layers reflect the electrochemical behavior of the pure metal components. The results are in agreement with the thermodynamic data.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
