Effect of oxidizing ions on corrosion rates of stainless steel in simulated solutions for reprocessing plants

Motooka, Takafumi; Yamamoto, Masahiro 

The corrosion behavior of stainless steel in nitric acid solutions has been usually investigated by short time corrosion tests. The change in corrosion rate with time has been not focused in these tests. In this report, the time-dependency of corrosion rate of stainless steel in nitric acid solution was investigated. Corrosion test of SUS304ULC stainless steel was conducted in boiling nitric acid solution containing Cr(VI) or V(V). The concentration of nitric acid solutions was ranged from 3 to 8 M, and the concentration of Cr(VI) or V(V) was ranged from 0.05 to 1 g/L. The samples of stainless steel were changed every 48 hours without renewal of the nitric acid solution during 240 hours. The obtained results were as follows; (1) The presence of Cr(VI) or V(V) in nitric acid solution accelerated the corrosion rate of stainless steel. The higher corrosion rate was observed in higher nitric acid concentration and greater content of Cr(VI) or V(V). (2) In boiling nitric acid solution with Cr(VI), the corrosion rate rapidly decreased in 8 M nitric acid solution. While in nitric acid solutions with V(V), the corrosion rate was little decreased. (3) The time-dependency of corrosion rates had a good correlation with corrosion potentials of stainless steel. Thus, the corrosion rate of stainless steel in nitric acid solutions with either Cr(VI) or V(V) would be controlled by corrosion potential.