Crevice corrosion of support alloys in the secondary environments of nuclear steam generators: Supplemental report: Final report

Technical Report · Sun Mar 01 04:00:00 EST 1987

OSTI ID:6332039

McKubre, M C.H.; Leach, S C

The extent to which a reduction in corrosion rate is possible by substituting alloys for carbon steel support plates in steam generators was estimated in this project. Galvanic corrosion currents were measured across crevices formed by alloy 600 tubes in support plate holes. Active galvanic cells are found between support alloys in crevices and alloy 600 tubes, both inside and outside the crevice. Both are important. The outside cell is driven by oxygen or oxidants in the bulk water. The effect of this external cell is to concentrate salt and acid in the crevice region, which may initiate aggressive damage due to the inside galvanic couple. By reducing the aggressive effect of oxidants outside the crevice, hydrazine can minimize the outside galvanic couple, and thus prevent the formation by electrochemical means of concentrated electrolyte condition in the crevice. The concentration of salts as well as pH are important factors in determining the galvanic corrosion rate inside the crevice. Concentrated seawater of near neutral pH was more corrosive than 10/sup -3/ normal sulfuric and hydrochloric acids or Susquehanna River water when pumped directly into the crevices. Compared to carbon steel, the corrosion rates were reduced about two- or fourfold for types 405 and 409 stainless steels and were reduced more than an order of magnitude by types 347 stainless steel and alloy 800. Acid chlorides were more corrosive to types 405 and 409 stainless steels than acid sulfates.

• Research Organization: SRI International, Menlo Park, CA (USA); Electric Power Research Inst., Palo Alto, CA (USA)
• OSTI ID: 6332039
• Report Number(s): EPRI-NP-5017; ON: TI87920303
• 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
ALLOYS
BOILERS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-NICKEL STEELS
COMPUTERIZED CONTROL SYSTEMS
CONTROL SYSTEMS
COOLING SYSTEMS
CORROSION
CORROSION RESISTANCE
CORROSION RESISTANT ALLOYS
CREVICE CORROSION
DATA ACQUISITION SYSTEMS
ELECTROCHEMICAL CORROSION
ELECTROLYTIC CELLS
ENERGY SYSTEMS
ENGINEERING
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HUMAN FACTORS ENGINEERING
IRON ALLOYS
IRON BASE ALLOYS
MAINTENANCE
MATERIALS
NICKEL ALLOYS
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
NUCLEAR FACILITIES
NUCLEAR POWER PLANTS
POWER PLANTS
RADIATION TRANSPORT
REACTOR COMPONENTS
REACTOR COOLING SYSTEMS
RELIABILITY
SECONDARY COOLANT CIRCUITS
STAINLESS STEEL-347
STAINLESS STEEL-405
STAINLESS STEELS
STEAM GENERATORS
STEELS
THERMAL POWER PLANTS
VAPOR GENERATORS