Experimental and theoretical study of inclusions during initiation of crevice corrosion
The initiation sites of crevice corrosion on stainless steel are generally recognized to be sulfide inclusions (MnS), although the mechanism by which the initiation occurs remains unknown. Controlled solution experiments showed that the products of the MnS electrochemical oxidation reaction were elemental sulfur and thiosulfate. Spectroelectrochemical cell experiments on MnS quantified the electrochemical production of thiosulfate. This finding linked the metallurgical and solution phases and suggested a depassivation mechanism based on a critical crevice solution composition. The range of thiosulfate and chloride ion concentrations in which the stainless steel oxide film remained passive was determined. All other species present in the crevice were shown not to influence depassivation. From the proposed mechanism a mathematical model was developed to determine the position and time of breakdown in the crevice based on transport of species by migration and diffusion, electrochemical kinetics, and potential field theory. Instrumented artificial crevices cell experiments were conducted to test the validity of the model and the proposed mechanism. The crevice cell geometry had a variable crevice height of 2.7 to 9.2 +- 0.2 ..mu..m and a depth of 1.27 cm; very good agreement between the experiments and the model was found for the conditions for avoiding crevice corrosion. The model was inverted in order to suggest the design criteria for achieving corrosion free crevices. 55 refs., 39 figs., 6 tabs.
- Research Organization:
- Illinois Univ., Urbana (USA). Graduate Coll.
- DOE Contract Number:
- AC02-76ER01198
- OSTI ID:
- 7128050
- Report Number(s):
- DOE/ER/01198-T24; ON: DE88014993
- Resource Relation:
- Other Information: Thesis (Ph.D.). Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
MANGANESE SULFIDES
OXIDATION
STAINLESS STEELS
CREVICE CORROSION
INCLUSIONS
ELECTROCHEMISTRY
EXPERIMENTAL DATA
MATHEMATICAL MODELS
SULFUR
THEORETICAL DATA
ALLOYS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISTRY
CHROMIUM ALLOYS
CORROSION
CORROSION RESISTANT ALLOYS
DATA
ELEMENTS
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
MANGANESE COMPOUNDS
NONMETALS
NUMERICAL DATA
STEELS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360105* - Metals & Alloys- Corrosion & Erosion