Corrosion Life-Time Assessment of Carbon Steel and Stainless Alloys for Geological Disposal Facilityby Akio Kosaki, CRIEPI, Chiba, Japan,
Hiroya Komada, CRIEPI, Chiba, Japan,
Abstract: The disposal facility for radioactive wastes, requires long-term integrity. Metal is considering to use as the engineered barrier which constructs the outer walls in such a facility, in order to prevent groundwater from percolating into such disposal facility. The present report discusses corrosion lifetime assessment of carbon steel and stainless alloys used for geological disposal facility. Potential-pH (E-pH) diagram for carbon steel is obtained in the environment of water which imitates groundwater in Japan. And the repassivation potential for crevice corrosion, ER, CREV is measured by an electro-chemical test. And the natural corrosion potential, ESP, and the repassivation potential for crevice corrosion, ER, CREV, for stainless alloys, Type 304 steel and Titanium alloys (ASTM Gr.1-Ti,Gr.12-Ti), are measured in the environment of neutral and alkalized water. And usable condition of these materials are discussed. The conclusion of this paper are: 1) In the environment of higher values of pH, carbon steel is in the state of passivation. In this state it can occure crevice corrosion, at least in the condition of [Cl-] ≥ 10ppm. So, using carbon steel is inadequate for coexistence with concrete lining which shows higher pH environment. In neutral pH environment which without concrete, carbon steel is in the state of uniform corrosion, and can be used by previous consideration of diminishing its thickness by corrosion, if the estimation of its thickness which depends on the accelerated tests are accepted. 2) Usable diagram for crevice corrosion of stainless alloys is obtained, which includes [Cl-] concentration and temperature as a parameter, and this diagram does not depend on any accelerated tests. And it can be said that the adequate selection of materials by using this diagram that is independent of time factor can assure long-term integrity for groundwater corrosion.
Subject Headings: Corrosion | Alloys | Carbon fibers | Stainless steel | Geology | Groundwater pollution | Groundwater flow | Radioactive wastes | Japan | Asia
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