Study of stainless steel corrosion by hydrogen measurement under deoxygenated, low-temperature and basic repository conditions

In the present study, corrosion tests of 18Cr-8Ni austenitic stainless steel were performed under assumed disposal conditions (dilute NaOH solution, pH 12.5, 303 K, Ar environment) by continuous measurement of gaseous hydrogen over 6.5 years through use of the gas flow system. The cumulative amount of hydrogen shows a good parabolic relationship against time until one year, followed by an approximately linear relationship. This suggests that the corrosion kinetics changes from an initial diffusion process to a linear rate law that holds for a long time. Assuming a corrosion reaction of 3Fe + 4H2O → Fe3O4 + 4H2, the corrosion rate decreases with time but after one year the rate remains constant at approximately 4 × 10−4 μm a−1 over the 6 next years.