Liquid-Air Interface Corrosion of A537 Steel in High Level Liquid Radioactive Waste Simulant in a Sealed Container

Abstract

Liquid-air interface (LAI) corrosion is regarded as a potential issue for interim storage tanks of high level liquid radioactive waste. Insightful studies have been carried out and several hypotheses have been proposed so far, while none has been directly confirmed experimentally. A sealed container has been developed to investigate the effect of atmosphere on LAI corrosion of partially immersed A537 steels, in which the composition and temperature of air can be changed accordingly, i.e. CO 2 concentration varied between 0.05 wt% (natural air) and 1.97 wt%, and temperature varied between 25 • C and 34 • C. It has been found that the pitting initiation process under both anodic polarization and free immersion conditions can be largely accelerated by the increase of CO 2 concentration. More importantly, a planar pH electrode has been applied to measure pH at the interface during anodic polarization and free immersion, and the occurrence of LAI corrosion can be correlated with the same interface pH at a certain temperature regardless of CO 2 concentration, indicating a "critical pH" for LAI corrosion determined by this method. This finding suggests that LAI corrosion in high level liquid radioactive waste may be investigated through determination of a critical pH in certain circumstances.

Microstructure Refinement on Crevice Corrosion of High-Speed Rail Steel U75V Visualized by an In Situ Monitoring System

“…This is related to the observation that those dark spots formed during free immersion can still be seen even after the expanding corroded area crossing them (Figure 7, 1 h). The appearance of dark color on the dissolved area (observed in macrographs) was mainly due to cementite, either detached from the surface or remained as a skeleton, which has been reported before on localized corrosion of industrial pure iron (Xu et al, 2017) and carbon steel (Xu et al, 2019).…”