Influence of nitrogen on electrochemical passivation of high-nickel stainless steels and thin molybdenum-nickel films
- State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering
The influence of molybdenum and nitrogen on passivation of the nickel-bearing austenitic stainless steels (SS) Fe-20% Cr-20% Ni, Fe-20% Cr-20% Ni-6% Mo, and Fe-20% Cr-20% Ni-6% Mo-0.2% N in deaerated 0.1 M hydrochloric acid + 0.4 M sodium chloride was investigated using electrochemical and X-ray photoelectron spectroscopy (XPS) analyses. Electrochemical analyses showed molybdenum and nitrogen improved passivation characteristics through an apparent synergism. Evidence was found of a compositional reorganization of SS in the atomic layers of the alloy immediately below the passive film. Nickel and molybdenum appeared to become enriched in proportions that suggested molybdenum-nickel intermetallic bonding. This was augmented by alloyed nitrogen, which strongly governed the elemental enrichment process. The possible nature of the bonding of these elements was revealed with respect to the Engel-Brewer model of intermetallic bonding. Variable-angle XPS and electrochemical polarization analysis in deaerated 0.1 M HCl was performed on a MoNi{sub 4} radio frequency (RF) sputtered thin film that simulated the commonly observed composition for such a sublayer alloy for a nitrogen-bearing SS. To simulate nitrogen segregation, electrochemical deposition of nitrogen was performed on thin films of MoNi{sub 4}. Following polarization of nitrided and non-nitrided films, variable-angle XPS showed the alloy surface underwent further changes resulting from nickel dissolution. The end-point composition of the alloy in each case below the passive film corresponded closely with known stable and intermediate intermetallic phases.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 187040
- Journal Information:
- Corrosion, Journal Name: Corrosion Journal Issue: 1 Vol. 52; ISSN 0010-9312; ISSN CORRAK
- Country of Publication:
- United States
- Language:
- English
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