気液交番環境における炭素鋼の腐食加速現象の研究,2; 鉄さび層の構造と加速機構

Study of the accelerated corrosion of carbon steel in air-solution alternating environment, 2; Iron rust structure and the acceleration mechanism

大谷 恭平   ; 塚田 隆 ; 上野 文義  ; 山本 正弘 

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi; Yamamoto, Masahiro

福島第一原子力発電所の格納容器内部を模擬した気中と水中へ交互に暴露される環境(気液交番環境)で炭素鋼の腐食は溶液中に比べて3倍以上加速されることが分かっているが、これまでの研究で腐食が加速する機構は明らかになっていない。本研究では気液交番環境で炭素鋼に形成した鉄さび層の断面観察および分析により、気液交番環境で炭素鋼の腐食が加速する理由は常に溶存酸素(DO)濃度の高い場所でカソード反応が生じ続ける構造の鉄さび層が形成するためであると考えられることを見出した。

It has been reported that the corrosion rate of carbon steel in air-solution alternating environment, however, the mechanism of the accelerated corrosion of carbon steel in the alternating environment has not been clarified. In the present study, the mechanism of accelerated corrosion of carbon steel in the alternating condition is investigated by the cross-sectional observation and analysis for rust layer formed on the steel after the corrosion tests. The observation and analysis showed that the multi-layered rust layer was formed on the steel in the alternating environment, and the multi-layer rust layer accelerated the cathodic reaction. This acceleration of the cathodic reaction is the reason why the corrosion rate of carbon steel was accelerated in air-solution alternating environment.