Corrosion mechanisms of carbon steel in the simulated air/solution interface

模擬気液界面における炭素鋼の腐食メカニズム

大谷 恭平   ; 加藤 千明   

Otani, Kyohei; Kato, Chiaki

福島第一原子力発電所1-3号機の格納容器(PCV)には、水素爆発防止や鋼材の腐食抑制のために冷却水が循環・注入されている。PCVの内部調査から、PCV内部の材料である炭素鋼は、空気と溶液の界面付近で気体と液体の環境が交互に変化する環境(気液交番環境)に曝されていることが確認された。金属材料は気液界面付近で薄い液膜に覆われており、鋼材表面に薄い液膜があると溶液中に比べて腐食速度が加速されることが報告されている。本発表では、1F PCV内の気液交番環境を模擬した回転腐食試験装置を用いて炭素鋼の腐食試験を行い、質量測定,観察,解析の結果から得られた炭素鋼の腐食速度と腐食機構を発表する。

Cooling water is circulated and injected into the containment vessel (PCV) of Fukushima Daiichi Nuclear Power Station (1F) Units 1-3, and nitrogen gas is injected and filled to prevent hydrogen explosion and to control corrosion of steel materials. In order to maintain the integrity of the PCV facilities over a long period of time until the decommissioning of the reactors, it is necessary to predict the corrosion behavior of carbon steel, which is the main structural material, and in particular to study the factors that may accelerate corrosion. From the internal investigation of the PCV, it was confirmed that carbon steel, which is the material inside the PCV, is exposed to an environment in which the gas and liquid environments alternate near the air/solution interface (Air/solution alternating environment). It has been reported that metallic materials are covered with a thin liquid film near the air/solution interface, and that the corrosion rate of steel is accelerated when there is a thin water film on the steel surface compared to that in solutions. In this presentation, the corrosion test of carbon steel was conducted using a rotating corrosion test apparatus to simulate the air/solution alternating environment inside the 1F PCV, and the corrosion rate and corrosion mechanism of carbon steel obtained from the results of mass measurement, observation and analysis will be presented.