RD&D-Programme 2004 - SKB

Programme
The ongoing experiments will be concluded during the period. The study of analogues will
continue during the period, provided that there are good study objects.
16.2.8 Corrosion of cast iron insert
If there is a penetrating breach in the copper shell, water can run into the gap between the
canister insert and the copper shell and further into the insert, where it can cause anaerobic
corrosion.
Conclusions in RD&D 2001 and its review
See section 16.2.7.
Newfound knowledge since RD&D 2001
The results of the past ten years’ research have been summarized in two articles published in
the journal Corrosion /16-7, 16-8/. Measurements of corrosion rates based on the amount of
hydrogen generated show initially high values of 10–30 microns per year, but after an oxide film
has formed the rate diminishes to less than 0.1 microns per year. The corrosion rate proved to be
independent of whether the material was immersed in water fully, partially or not at all. Another
conclusion drawn from the experiments was that hydrogen pressures of up to 100 bar had no
effect on the corrosion rate. No local corrosion was initiated under anaerobic conditions.
A study of corrosion of iron in contact with bentonite is currently being conducted. The initial
results show a slightly higher corrosion rate than has been measured in the absence of bentonite
/16-9/. It has not yet been clarified whether this increase is due to the interaction between the
minerals in the bentonite or whether it is caused by the fact that the bentonite pore water has a
different composition than the types of water used in the earlier experiments, where the water
composition was found to be of some importance for the corrosion rate.
Programme
Since the water composition in the experiments turned out to be of some importance for the
corrosion rate, further experiments with other water types will be carried out during the period.
The investigation of corrosion of iron in contact with bentonite will continue during the period.
During the preceding period, an investigation of anaerobic corrosion of iron in a gamma
radiation field was started. The investigation is still going on and will be concluded during 2005.
16.2.9 Galvanic corrosion
Metallic contact between cast iron and copper is a precondition for galvanic corrosion.
Conclusions in RD&D 2001 and its review
See section 16.2.7.
Newfound knowledge since RD&D 2001
A project for determining any effects of metallic coupling between copper and cast iron on the
corrosion rate was started in 2001. The final report on the project will be published during 2004
/16-10/. The results obtained so far show that even if corrosion rates of up to 100 microns per
year could be measured under oxygenated conditions, the rate under oxygen-poor conditions
188 RD&D-Programme 2004