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U.S. Department of Energy
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How to simulate acid corrosion of Alloy 600 steam generator tubes

Book ·
OSTI ID:203813
;  [1]; ;  [2];  [3]
  1. Laborelec, Linkebeek (Belgium)
  2. Materials Engineering Associates, Inc., Lanham, MD (United States)
  3. Electric Power Research Inst., Palo Alto, CA (United States)
Laborelec and MEA have completed a series of steam generator (SG) tube capsule tests to further assess the effects of acidified environments on wastage, intergranular attack (IGA) and stress corrosion cracking (SCC) in alloy 600 tubing. Most of the tests were performed with deaerated solutions containing magnetite, sodium silicate and cationic resin beads. The results from the two laboratories were remarkably coherent and showed deep, intergranular SCC with only minor occurrence of IGA or wastage, together with thick Cr enriched oxide layers, in good agreement with the secondary side corrosion morphology at Doel 4 or other Belgian plants. High cracking rates were obtained, up to 5 {micro}m/h (45 mm/y). The only influence of lead addition was to increase slightly the cracking rate in lesser-strained areas, which also supports plant observations. A similar effect was observed for organics coming from the decomposition of the resin beads, as shown by comparison with the results obtained by replacing the resins by their calculated sulfate equivalent. Addition of a previously investigated solution of chlorides and sulfates to the resin solution further increased the cracking rate up to 20 {micro}m/h. However, the presence of carbon steel coupons in the capsules appeared to completely inhibit SCC of the alloy 600 tubes, which was not the case for the initial resin or sulfate solutions (without chlorides). In less concentrated sulfuric and/or acetic acid solutions containing magnetite, producing lower intergranular cracking rates, the addition of lead had a marked influence on the mode of cracking, which became partially transgranular. Here again, the maximum cracking rate was not modified but SCC was enhanced in lesser-strained areas.
OSTI ID:
203813
Report Number(s):
CONF-950816--; ISBN 1-877914-95-9
Country of Publication:
United States
Language:
English