Corrosion Behavior of SUS 304 Stainless Steel in Sulfuric Acid-Cerium (IV) Solution

The corrosion behavior of SUS 304 stainless steel in sulfuric acid-cerium (IV), SC, solution with and without the electrolytic regeneration of Ce4+ from Ce3+ has been investigated in connection with developing a chemical decontamination process for nuclear facilities. The corrosion rate was determined from the amounts of dissolved metal ions, Fe, Cr and Ni: The relative composition was the same as that of SUS 304. Namely, no preferential dissolution of any component occurred. Without the electrolytic regeneration both the corrosion rate and Ce4+ concentration decreased during corrosion test. The observed amounts of Ce4+ consumption were in good agreement with those calculated from the amounts of the dissolved metal ions on the assumption that their ionic forms were Fe3+, Cr (VI) and Ni2+ in the SC solution. The electrolytic current required to maintain the Ce4+ concentration to be constant during corrosion test can be calculated from the corrosion rates, composition and surface areas of alloys. The corrosion rate is slightly smaller in the mixture of Ce3+ and Ce4+(Ce4+/Ce3+<1) than in the solution without Ce3+, and in both cases, the corrosion rate shows first order dependence on Ce4+ concentration (1.3-10×10-3M Ce4+ in 0.25M H2SO4) in the temperature range 40-80°C, but is little affected by Ce3+ concentration (5-95×10-3M).