Influence of Temperature on Stress Corrosion Cracking Susceptibility of Carbon Steel in Sodium Hydrogen Carbonate Aqueous Solution Assuming Upper Limit of Carbonate Concentration in Geological Disposal Environment

Slow strain rate test （SSRT） was performed for a rolled carbon steel in NaHCO3 aqueous solutions at various temperatures in the range of 303-393 K. Selected concentrations of NaHCO3 between 0.1 and 0.5 mol･dm－3 are assumed to be the upper limit of carbonate concentration in groundwater in a geological disposal environment. As the results, no obvious influence of temperature on mechanical properties such as fracture strain ratio were observed, but SCC susceptibility based on ratio of SCC fracture area increased at relatively low temperatures of 303 K and 323 K. It was suggested that the reason for the higher SCC sensitivity of the steel at lower temperatures was due to slower repassivation at lower temperatures. Regarding the type of SCC, intergranular SCC was dominant at low temperatures and tended to transition to transgranular SCC at higher temperatures.