2010 Volume 59 Issue 11 Pages 418-429
Immersion tests of carbon steel were performed in compacted bentonites saturated with simulated groundwater for a 10-year duration under anaerobic condition. The ferrous carbonates were identified as the corrosion product by XRD and XPS analyses in most of the test cases. The amount of corrosion in high carbonate concentration was smaller than those under the other test conditions throughout the test periods. Although the corrosion rate at 50°C was initially smaller than that at 80°C, it resulted in larger value after several years. The effects of carbonate content and temperature on the long-term corrosion rate seemed to be correlated to the behavior of deposition of the iron carbonate on the surface of carbon steel. Additionally, the correlation between initial corrosion rate and the protectiveness of corrosion product film was examined. Except for high carbonate condition, as the initial corrosion rate 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 in good agreement with that of archaeological analogue data.