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

Otani, Kyohei   ; Kato, Chiaki   

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.