采用原位电化学监测技术研究了SO₄^2-对NiCu低合金钢在除氧NaHCO₃溶液浸泡过程中腐蚀行为的影响, 并利用XRD和SEM对浸泡后样品的锈层相结构和表面形貌进行了分析. 结果表明, 与纯NaHCO₃溶液相比, SO₄^2-的添加会在浸泡初期加速基体的腐蚀, 在后期抑制保护性腐蚀产物膜的生成, 促使腐蚀模式由未加入SO₄^2-时的预钝化行为向活性溶解转变. 此外, SO₄^2-与HCO₃^-浓度的升高均有助于Fe₆(OH)₁₂CO₃的生成. 样品表面腐蚀产物最终由a-FeOOH, Fe₃O₄和Fe₆(OH)₁₂CO₃构成, 表面形貌均以均匀腐蚀为主.

High level radioactive waste (HLW) is an extremely dangerous by-product of the global nuclear industry. Due to its intensely radioactive nature and ultra long half-life, HLW has to be safely managed and disposed for thousands of years, isolated from the biosphere. Deep geological repository (DGR) is considered to be the most feasible option worldwide because of its operability, stability, durability, environmental protection and so on. Basically, DGR relies on a multibarrier system and it consists of metallic canisters, backfill materials and a stable geologic formation. Since radionuclides could be moved into the biosphere by action of groundwater, both the geologic formation and backfill materials have to be of very low hydraulic permeability and metal canisters have to be corrosion resistant and prevent contact between the groundwater and the radioactive waste for as long as possible. Low carbon steel has been selected and studied as a candidate canister material in many countries because its long industrial experience, high-strength, low cost and it is less prone to localized corrosion than materials that passivity, but its larger corrosion rate may also set an insuperable barrier for the practical application. Recently, our studies revealed that NiCu low alloy steel is a more promising candidate for the canister material compared with the popular one, low carbon steel, since the former performs a more acceptable corrosion rate without increasing much cost and has better resistance to localized corrosion in environments with high concentration of Cl^-. In this work, effects of SO₄^2-, another ubiquitous species in deep groundwater, on the corrosion behavior of NiCu low alloy steel during immersion in simulated deep groundwater environments were investigated by in situ electrochemical measurements and surface analysis techniques. Results show that the addition of SO₄^2- can promote the substrate dissolution during the initial stage of immersion. In the later stage, SO₄^2- weakens the protectiveness of formed films and consequently, active dissolution prevails on the electrode surface rather than the prepassivation. Concentrated SO₄^2- and HCO₃^- can both promote the formation of Fe₆(OH)₁₂CO₃. The main components of corrosion products are a-FeOOH, Fe₃O₄ and Fe₆(OH)₁₂CO₃, and uniform corrosion is observed.