In this study, a corrosion inhibitor suitable for the corrosion inhibition of primary containment vessels at the Fukushima Daiichi Nuclear Power Station is investigated. Considering the internal environment of the primary containment vessels, the corrosion inhibitor should inhibit the freshwater corrosion of carbon steel under irradiation and should not come under effluent standards in Japan. Herein, a corrosion inhibitor was devised by combining Al lactate and Na molybdate that met the above conditions, and its corrosion mechanism was investigated. It was found that 0.75 mM Al lactate and 0.25 mM Na molybdate were the most inhibitive to the corrosion of carbon steel. As Al lactate has never been reported as a corrosion inhibitor for metallic materials, it could be developed as a novel corrosion inhibitor in this study. The corrosion inhibitor inhibited the freshwater corrosion of carbon steel even under gamma irradiation of 200 Gy/h. Al and molybdate ions in the solution formed a metal cation layer on carbon steel with few defects and without iron. This metal cation layer inhibited both the cathodic oxygen reduction reaction and the anodic iron dissolving reaction, thereby enhancing the corrosion protection of carbon steel in freshwater.

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