Canister materials corrosion experiment

Environmental effects on the fracture of pure OFHC-copper have been studied by using a slow strain rate testing (SSRT) method in simulated ground water conditions and in nitrite solutions. Tests at room temperature produced ductile dimpled fracture and the elongation to fracture was about 35%. However, tests at 80 deg C performed in distilled water and in glycerin produced intergranular ductile fracture and the elongation to fracture was reduced to 24%. The intergranular ductile fracture of pure OFHC-copper at 80 deg C was influenced by the chemical composition of the environment. Additions of chlorides and sulfates to the ground water environment further decreased the elongation to fracture obtained in SSRT-tests to 14%. These results are interpreted by environment sensitive creep phenomenon. Tests were also performed in nitrite environment (0.3 M NaNO2) where transgranular stress corrosion cracking was produced. The tests were conducted also at various potentials in order to determine the threshold potential for cracking