Diffusion behavior of DO in the film on Fe oxidized at high temperature in air

Haruna, Takumi*; Yamamoto, Tatsuya*; Miyairi, Yoji*; Shibata, Toshio*; Taniguchi, Naoki ; Sakamaki, Keiko ; Tachikawa, Hirokazu*

Diffusion coefficients of DO in the films was determined in order to estimate corrosion rate of carbon steel for the overpack in ground water. Fe plates were heated to form oxide films. The films were characterized with XRD and SEM. After that, the specimen was contacted with DO for 5184 ks, followed by subjected to TDS to obtain an amount of DO absorbing into the film. As a result, single-layered film of FeO was formed at 573 and 723 K, and double-layered film of FeO and FeO was formed at 873 K. It was found that an amount of DO in the film correlated linearly with a square root of the absorption period, and that the amount was steady for a long period. From the results and Fick's second law, diffusion coefficients of DO was determined as 9.710 cms for the FeO film, and 5.510 cms to 2.210 cms for FeO film.