Micromorphology and microchemistry of corrosion products in tubesheet crevices: Final report

Technical Report · Tue Sep 01 04:00:00 EDT 1987

OSTI ID:6057749

Gibbon, D L; Varsanik, R G

Microchemical and micromorphologic examinations have been made on tubes of mill annealed alloy 600. On one tube, intergranular attack (IGA) was very light; major attention was directed instead to the denting magnetite formed by alkali in the tube-tubesheet crevice. Magnetite at the top of the tubesheet is coarsely crystalline at the Inconel contact surface (ICS), with large open channels available for passage of liquid phases. Na, Si, and S are major constituents of crystalline phases with magnetite. The second tube exposed to alkaline silicate showed very little IGA, while the third tube exposed to alkaline sulfate showed from 200 to 300 micrometers of attack. The final sample included both tube and tubesheet. The crevice was filled with magnetite and (Na, P)-rich needle-like crystals. Cr, Ni, Ti, Ca, Cl, S, P, Si, K and Na are all found in addition to the expected Fe. The tube scale is highly porous. IGA affects approximately 60% of the tube wall thickness. The intergranular surfaces in the tube are commonly covered with easily seen films/deposits. 2 refs., 26 figs., 5 tabs.

• Research Organization: Calgon Corp., Pittsburgh, PA (USA); Electric Power Research Inst., Palo Alto, CA (USA)
• OSTI ID: 6057749
• Report Number(s): EPRI-NP-5400; ON: TI88920039
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220200* -- Nuclear Reactor Technology-- Components & Accessories
36 MATERIALS SCIENCE
360105 -- Metals & Alloys-- Corrosion & Erosion
ALKALI METALS
ALKALINE EARTH METALS
ALLOYS
BOILERS
CALCIUM
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
CHROMIUM ALLOYS
CORROSION
CREVICE CORROSION
ELECTRON MICROSCOPY
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
INCONEL 600
INCONEL ALLOYS
INTERGRANULAR CORROSION
IRON ALLOYS
METALS
MICROSCOPY
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
NONMETALS
SCANNING ELECTRON MICROSCOPY
SEMIMETALS
SILICON
SODIUM
STEAM GENERATORS
STRESS CORROSION
SULFUR
TUBES
VAPOR GENERATORS