Stress corrosion cracking (SCC) of oxygen‐free phosphorous‐alloyed copper was investigated in sulphide‐ and chloride‐containing deoxygenated water at 90°C with sulphide concentrations of 0.001 and 0.00001 M. Several intergranular defects were found in the specimen exposed to the high sulphide environment. Similar defects were not found in the low sulphide environment, where only slight corrosion on grain boundaries and slip lines occurred. Hydrogen content measurements show an increase in hydrogen uptake of the plastically deformed specimens, which is dependent on the sulphide concentration and on plastic deformation of copper. However, the highest hydrogen content was measured in friction stir welds, welded in air without shielding gas, and tested in the high sulphide environment. The embedded oxide particles in the weld metal act as local hydrogen trapping sites and selectively react with the sulphide solution. A relatively thick air‐formed oxide film covers the copper canisters when deposited, which transforms into a sulphide film in the repository conditions. Thus, some of the coupon specimens were pre‐oxidised. The conversion of the pre‐existing Cu2O film into Cu2S film occurs quickly and the transformation is almost 100% efficient. The structure and properties of the Cu2S films, susceptibility of copper to sulphide‐induced SCC and hydrogen uptake of copper in reducing, anoxic repository conditions are discussed.

The freeze lining of an industrial copper flash smelting furnace slag, its growth kinetics and microstructure have been studied using a water cooled probe technique in a rotating crucible furnace at 1350uC. The first layers of iron silicate slag solidify on the water cooled metal surface as amorphous or glassy material with a minor fraction of crystalline spinel phase precipitated. At a distance of 4-5 mm from the cold face about 50% of the structure is composed of crystalline olivine (fayalite) and spinel phases embedded in a glassy matrix. Major thickness of the freeze lining is formed within first 15 min of slag contact with a cooled metal surface. The solidified microstructures obtained were compared with equilibrium phase assemblages calculated. The equilibrium solidification in the near solidus reactions includes the formation of pyroxene and rhodonite type phases, but they were not identified in the lining microstructures.

The KBS-3 method for long-term disposal of spent nuclear fuel is designed with an external self-standing copper shell, which provides the most important barrier against corrosion and escape of radionuclides, and an internal nodular cast iron insert, which provides the load-bearing structure against external loads. The material intended for the load-bearing insert is ferritic nodular cast iron EN 1563 grade EN-GJS-400-15U. In this paper, hydrogen uptake and sensitivity to hydrogen-induced cracking of the cast iron were studied using tensile testing under continuous electrochemical charging in 1 N H2SO4 solution. Hydrogen uptake was measured by using the thermal desorption method. It was found that the hydrogen desorption profile manifests three distinct peaks at initial locations of 400, 500, and 700 K with a heating rate of 6 K/min. Plastic deformation results in a remarkable increase of the 400 K peak, which indicates hydrogen uptake during deformation. In the constant extension rate tests (CERT) and the constant load tests (CLT), electrochemical hydrogen charging reduced markedly the elongation to fracture and time to fracture, respectively. In CLT, hydrogen charging increased dramatically the creep rate at the applied load of about 0.7 yield stress. Ligaments between the graphite nodules exhibit brittle cleavage facets in the presence of hydrogen, while the ligaments show a characteristic ductile appearance of shear and small dimples when testing in air or distilled water. The obtained results are discussed in terms of the known mechanisms of hydrogen-induced cracking and the role of the graphite nodules in the embrittlement of ductile cast iron.

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