The Corrosion rate and the hydrogen absorption behavior of titanium under anaerobic condition

Suzuki, Hiroyuki*; Taniguchi, Naoki 

Titanium is one of the candidate materials for overpacks as a high corrosion resistance metal. Hydrogen embrittlement is a main cause of the damage of long term integrity of titanium overpack. It is not well known about the corrosion resistance and hydrogen absorption behavior of titanium under anaerobic condition. In this study, the completely sealed ampoule test and the immersion test of titanium was carried out in aqueous solution and bentonite in order to obtain reliable data about the hydrogen generation rate and the ratio of hydrogen absorption in titanium. As the results of the tests with changing the environmental factors, obvious higher corrosion rates were observed at high carbonate (1M) and high pH(pH13) conditions due to the increase in the anodic reaction rate. In other conditions, corrosion rate of titanium were estimated to be in the order of 10 10 m/y. Almost all (98%) of the hydrogen generated by corrosion was absorbed into titanium. Assuming that the time evolution of the hydrogen content in titanium follows linear law to make conservative assessment, the absorbed hydrogen content was estimated to be of 400 500ppm in 1000 years.