Passivation behavior of mild steel used for nuclear waste disposal package
Mild steel has been investigated as one of the overpack materials for geological disposal of high-level nuclear waste. The present paper discussed the passivation behavior of mild steel using an electrochemical approach to evaluate the critical condition for passivation. The critical current density for passivation, i{sub crit}, of mild steel in 0.1 mol/L [HCO{approximately}{sup {minus}} + CO{sub 3}{sup 2{minus}}] solution at room temperature was found to decrease with increasing pH of the solution. The depassivation pH, pH{sub d}, at room temperature was determined to be about 7.5 by comparisons between i{sub crit} and the diffusion-limiting current density, i{sub L}{sup 02}, for dissolved oxygen of 8.1 ppm in equilibrium with atmospheric oxygen. The anodic current density of mild steel in the solution of pH = 8 at 90 C was also measured and was found to decrease rapidly with time, leading to the absence of a critical current density for passivation. Thus, mild steel can be self-passivated in the system. An empirically determined corrosion phase diagram is provided for mild steel in 0.1 mol/L [HCO{sub 3}{sup {minus}} + CO{sub 3}{sup 2{minus}}] solution at 90 C, based on these findings and some published data.
- Research Organization:
- Ishikawajima-Harima Heavy Industries Co., Ltd., Koto, Tokyo (JP)
- OSTI ID:
- 20015841
- Resource Relation:
- Conference: 1998 Materials Research Society Fall Meeting, Boston, MA (US), 11/30/1998--12/04/1998; Other Information: Single article reprints are available from University Microfilms Inc., 300 North Zeeb Road, Ann Arbor, Michigan 48106; PBD: 1999; Related Information: In: Scientific basis for nuclear waste management XXII. Materials Research Society symposium proceedings: Volume 556, by Wronkiewicz, D.J.; Lee, J.H. [eds.], 1355 pages.
- Country of Publication:
- United States
- Language:
- English
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