Corrosion Behavior of Low-Carbon Steels in Grande Ronde Basalt Groundwater in the Presence of Basalt-Bentonite Packing

摘要

Three low-carbon steels (AISI 1006, AISI 1020, and AISI 1025) were tested at 150 exp 0 and 250 exp 0 C in Hanford Grande Ronde Basalt groundwater (9.75) pH) under anoxic conditions (less than or equal to 0.1 mg/L oxygen in water) in packing (75 wt% basalt + 25 wt% bentonite) for 1 and 2 weeks. Testing was initially performed in air-equilibrated groundwater (oxic conditions) without packing at 150 exp 0 C. The average corrosion under anoxic conditions with packing was at least a factor of seven lower than that for oxic conditions at 150 exp 0 C. The data indicated that carbon composition apparently affects the corrosion of low-carbon steel under oxic conditions. Under anoxic conditions with packing, corrosion was independent of the carbon composition of the steel as evidenced by almost equal weight losses for all three steels at 150 exp 0 and 250 exp 0 C. The weight loss at 250 exp 0 C was about the same as that at 150 exp 0 C due to the formation of a very adherent layer of iron-rich clay on the surface of the steel at 250 exp 0 C, reducing the rate at which corrosion proceeds. Pitting was not detected in any of the specimens. Assuming linear corrosion kinetics, extrapolation of the 2-week data to 1,000 yr resulted in approximately 12 mm penetration of the low-carbon steel in Grande Ronde Basalt groundwater under anoxic conditions with packing. (ERA citation 09:028792)