Effect of applied potential on changes in solution chemistry inside crevices on type 304L stainless steel and alloy 825

Journal Article · Mon Oct 31 23:00:00 EST 1994 · Corrosion (Houston); (United States)

DOI:https://doi.org/10.5006/1.3293476· OSTI ID:6673468

Sridhar, N; Dunn, D S ^[1]

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1. Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

Changes in pH, chloride (Cl) concentration, and potential inside a rectangular crevice of metal against polymethyl methacrylate (PMMA) were monitored using microelectrodes as a function of time and externally applied potential. The environment inside the crevice was altered within the experimental time frame only when the external potential was maintained above a certain value. When the external potential exceeded that value, there was an incubation period followed by a rapid increase in current density. This event was succeeded by a decrease in pH and potential inside the crevice. The current density also decreased rapidly upon reversal of the external potential, while a significant reversal of pH occurred over a much longer time. The kinetics of these changes in environment were functions of crevice tightness. A decrease in crevice gap resulted in a greater decrease in pH. Changes in Cl concentration were much more modest, perhaps because of formation of Cl complexes that could not be detected by the silver-silver chloride microelectrode. Chromium depletion on the surface of alloy 825 (UNS N08825) in the crevice resulted in a more rapid decrease in pH even when the surface was rougher. These observations were explained in terms of crevice corrosion nucleation in narrow gaps between peaks of surface asperities, which then propagated laterally to adjoining wider gaps between the peaks and valleys of the asperities.

• OSTI ID: 6673468
• Journal Information: Corrosion (Houston); (United States), Journal Name: Corrosion (Houston); (United States) Vol. 50:11; ISSN 0010-9312; ISSN CORRAK
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOY-NI43FE30CR22MO3
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
AUSTENITIC STEELS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
CHROMIUM ALLOYS
CHROMIUM-NICKEL STEELS
CONCENTRATION RATIO
COPPER ALLOYS
CORROSION
CORROSION RESISTANT ALLOYS
CREVICE CORROSION
ELECTRIC POTENTIAL
ELECTROCHEMICAL CORROSION
HALIDES
HALOGEN COMPOUNDS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HIGH ALLOY STEELS
INCOLOY 825
INCOLOY ALLOYS
IRON ALLOYS
IRON BASE ALLOYS
KINETICS
LOW CA
MATERIALS
MOLYBDENUM ALLOYS
NICKEL ALLOY
NICKEL ALLOYS
NICKEL BASE ALLOYS
PH VALUE
REACTION KINETICS
STAINLESS STEEL-304L
STAINLESS STEELS
STEEL-CR19NI10-L
STEELS