EFFECT OF ADDITION OF SODIUM TUNGSTATE AND ZINC/SODIUM MOLYBDATE MIXED PHOSPHATE ON CORROSION OF CARBON STEEL UNDER DILUTED ARTIFICIAL SEAWATER ENVIRONMENT

摘要

Fukushima Daiichi nuclear power plants (1F) were damaged by unprecedented severe accident in the great east Japan earthquake on 11th, March, 2011, and seawater had been injected as an emergency countermeasure for the core cooling. Because the primary containment vessel (PCV) is important equipment for cooling and removal of fuel debris, it is necessary to maintain the structural integrity of the PCV for a long period. Since the PCV is made of carbon steel, it is necessary to develop the countermeasure for corrosion inhibition of carbon steel. In this study, sodium tungstate and zinc/sodium molybdate mixed phosphate were selected as the corrosion inhibitor. Immersion corrosion tests of carbon steel of PCV material under 1F cooling water simulated environment with addition of the corrosion inhibitors were carried out. As a result, the corrosion mass loss of carbon steel with polishing surface was decreased by addition of each corrosion inhibitors. In addition, in the case of carbon steel covered with corrosion product, it was necessary to increase the concentration in sodium tungstate for corrosion inhibition, but it was not necessary to increase the concentration of zinc/sodium molybdate mixed phosphate for corrosion inhibition.