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Effects of Anionic Species on the Polarization Behavior of Copper for Waste Package Material in Artificial Ground Water

Published online by Cambridge University Press:  15 February 2011

Hachiro Imai
Affiliation:
Shibaura Institute of Technology, Tokyo, JAPAN
Takanori Fukuda
Affiliation:
Ishikawajima-Harima Heavy Industries (IHI) Co., Ltd., Tokyo, JAPAN
Masatsune Akashi
Affiliation:
Ishikawajima-Harima Heavy Industries (IHI) Co., Ltd., Tokyo, JAPAN
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Abstract

The effects of HCO3, Cl, and SO42- on copper as a candidate material for overpacking for geological disposal of high level radioactive wastes are studied at 303 K in dissolved oxygen(DO)- controlled, ground-water simulating aqueous solutions by using a cyclic polarization curve method.

Two types of polarization curve were determined: Type A in which free corrosion proceeds in the active dissolution mode, and Type P in which passivation takes place in a potential domain characterized by a potential that corresponds to Eb, the potential at which the passivated film is broken. Polarization dependence on DO was also determined: when only HCO3 is present, a Type A curve results for DO < 0.5 ppm when HCO3 = 10 – 300 ppm, transiting to a Type P curve when HCO3 > 3,000 ppm; when DO < 15ppm, however, a Type P results for HCO3 ≤ 10 ppm; when either Cl or SO42- coexists with HCO3, HCO3 promotes passivation while Cl- and SO42- promote active dissolution, the influence of Cl being greater than that of HO42- if HCO3 content is constant. The presence of either CI or SO42 over 100 ppm makes the curve Type A irrespective of DO, both species shifting Eb toward the less noble direction.

The constant potential test shows that the passivated film of copper is easily broken if Cl is present.

Type
Research Article
Copyright
Copyright © Materials Research Society 1996

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