Composition changes around sulphide inclusions in stainless steels, and implications for the initiation of pitting corrosion
Abstract
We report high-resolution SIMS microscopy measurements, which show that many 'MnS' inclusions have surrounding them a narrow 'halo' of half-width typically 100 nm that is strongly enriched in Fe, forcing consideration of the electrochemistry of FeS as a determinant of the behaviour of the inclusion boundary. We suggest that on exposure to water a very thin and porous metal-deficient polysulphide skin forms between the bulk of the inclusion and the steel, within which a pit can be triggered. The results resolve a controversy concerning the composition of the boundary region around inclusions in stainless steel and re-emphasise its potential significance.
- Publication:
-
Corrosion
- Pub Date:
- 2010
- DOI:
- 10.1016/j.corsci.2010.07.021
- Bibcode:
- 2010Corro..52.3702W
- Keywords:
-
- A. Stainless steel;
- B. SIMS;
- B. XPS;
- C. Pitting corrosion;
- C. Segregation;
- C. Inclusion