Electrochemical Corrosion Behavior of Low-Carbon I-Beam Steels in a Simulated Yucca Mountain Repository Environment

The electrochemical corrosion behavior of low-carbon steel (CS) was examined in a simulated Yucca Mountain (YM) groundwater by varying the electrolyte concentration and temperature under aerated and deaerated conditions. The results show that in deaerated conditions, the corrosion rate is low, in the order of 0.6 mpy to 4.5 mpy, between 25°C to 85°C, respectively, whereas for aerated conditions the measured rates increased to 3 mpy to 55 mpy. The rates initially increased with temperatures up to 45°C, and a decreasing trend was observed with a further increase in temperature from 65°C to 85°C. The maximum corrosion rate occurred at 45°C (54.5 mpy). The low corrosion rates observed in all deaerated conditions and in aerated solutions at higher temperatures were due to the formation of Mg species on the steel surface, as identified by x-ray photoelectron spectroscopy analyses. The results also indicate possible localized corrosion behavior of CS in aerated conditions up to 45°C.