Corrosion behavior of carbon steel in compacted bentonite saturated with simulated groudwater under anaerobic condition

Taniguchi, Naoki ; Kawasaki, Manabu; Naito, Morimasa 

Immersion tests of carbon steel were performed in compacted bentonite for 10 years duration under anaerobic condition. The ferrous carbonates were identified as the corrosion product by XRD and XPS analysis in almost test cases. The amount of corrosion in high carbonate concentration was smaller than those of other test conditions throughout the test periods. Although the corrosion rate at 50C was initially smaller than that at 80C, it resulted in larger value after several years. Such the effects of carbonate content and temperature on the long-term corrosion rate seemed to be correlated to the behavior of dissolution/precipitation of iron carbonate. Additionally, the correlation between initial corrosion amount and the protectiveness of corrosion product film was examined. Except for high carbonate condition, as the corrosion amount at early stage of immersion was larger, the corrosion product film tended to become more protective. The long-term corrosion depth was estimated by the extrapolation of the laboratory test results. The range of the estimated value was well agreed with that of archaeological analogue data.