Effects of Different Ions and Temperature on Corrosion Behavior of Pure Iron in Anoxic Simulated Groundwater

Abstract

As a typical material of the insert in high-level radioactive waste (HLW) geological disposal canisters, iron-based materials will directly contact with groundwater after the failure of a metallic canister, acting as a chemical barrier to prevent HLW leaking into groundwater. In this paper, anoxic groundwater was simulated by mixing 10 mM NaCl and 2 mM NaHCO3 purged by Ar gas (containing 0.3% CO2) with different added ions (Ca2+, CO32− and SiO32−) and operation temperatures (25, 40 and 60 °C). An electrochemical measurement, immersion tests and surface characterization were carried out to study the corrosion behavior of pure iron in the simulated groundwater. The effects of Ca2+ on the corrosion behavior of iron is negligible, however, Cl− plays an important role in accelerating the corrosion activity with the increased concentration and temperature. With increased concentrations of CO32− and SiO32−, the corrosion resistance of iron is largely improved, which is attributed to the formation of a uniform passivation film. The independent effects of temperature on the corrosion behavior of iron are resulted from the repeated passivation–dissolution processes in the formation of the passivation film, resulting from the synergistic effects of CO32−/SiO32− and Cl−. The formation of ferric silicate is dominant in the passivation film with the addition of SiO32−, which effectively protects the iron surface from corrosion.

Effect of Chloride Ions on Electrochemical Behavior of Canister Materials

“…It was also observed that the potential range decreased above the corrosion potential, wherein the anodic current density increased rapidly. is result shows the aggressiveness of chloride ions; the corrosion potential decreases, and the current density increases with the addition of chloride ions [12]. e corrosion potentials and currents of the test materials are listed in Table 2.…”

Effects of Corrosion Products Deposited on 304 Stainless Steel on Reduction of Se (IV/VI) in Simulated Groundwater

“…After the addition of Na 2 SiO 3 , corrosion products were mainly composed of Fe, O, and Si, indicating that SiO 3 2− was involved in the corrosion reaction. Moreover, Fe-based compounds in the corrosion products mainly contained Fe(II) and Fe(III) elements, such as FeO and Fe 3 O 4 [2]. It is noticeable from Figures 3 and 4 that, after being treated by polarization m urements in the SG solution, corrosion products were mainly composed of Fe and O. being treated by polarization measurements in the SG + CaCl2 solution, corrosion p ucts generated on the steel surface were mainly composed of Fe, O, and Ca, and they mainly calcium-rich products and Fe-based compounds, indicating that Ca 2+ ions involved in the corrosion reaction.…”

“…Deep geological disposal is widely accepted by major nuclear power countries in the world to isolate radionuclides permanently from the biosphere [1,2]. 79 Se is considered a key mobile fission product for the geological disposal of nuclear waste.…”

“…Mingliang Kang et al [5] investigated the influence of pH and reaction time on the formation of FeSe 2 by reductive precipitation of Se(IV) with nanosized pyrite-greigite; they found that FeSe 2 was formed at pH > 6.07. Teng Li et al [2] found that an Fe(II) compound-containing passivation film was formed on the surface of pure iron in simulated groundwater containing carbonate, silicate, and calcium ions.…”

Corrosion behavior and mechanism of ductile iron with different degrees of deterioration of cement mortar lining in reclaimed water pipelines

“…The SiO 3 2À dissolved from the CML also helped to form a uniform passive lm, and played an important role in improving the barrier effect of the iron surface. 28 Therefore, the process of electron loss in ductile iron was the determining step of corrosion under the barrier of the lining. Additionally, the Bode plot (Fig.…”