海洋环境腐蚀与生物污损重点实验室知识库

深地质处置法是目前处置高放射性核废料最可靠的方法，该方法拟将核废料封存在金属储罐中，罐身周围包裹缓冲材料，埋于距地下500~1000米深的处置库中。其中，金属储罐是隔绝核废料与人类生活圈最重要的人工屏障。经过多年考察，我国已经选择甘肃北山地区为深地质处置库的预选场址，但封存核废料金属储罐的材料选择和耐蚀设计仍然悬而未决，碳钢内胆加铜外层的“双重壁”储罐设计备受关注。当铜外层破损导致铜与碳钢同时暴露在地下水中时，铜和碳钢存在发生严重电偶腐蚀的风险，这将加快碳钢内胆的腐蚀速率。因此，铜与碳钢在深地质环境中的电偶腐蚀行为研究，是“双重壁”储罐设计、安全评估的重要内容。

本论文通过模拟北山深地质环境，利用腐蚀电化学手段，研究铜/碳钢面积比、温度、氧含量和溶液离子浓度变化对T2铜和Q235碳钢电偶腐蚀电流密度和电偶电压的影响；利用SEM、EDS、Raman和XPS等表面分析技术，分析Q235碳钢表面腐蚀产物，发现铜与碳钢电偶腐蚀机理及影响因素。

本论文第2章研究了铜/碳钢面积比、温度和氧含量变化对T2铜和Q235碳钢电偶腐蚀行为的影响。研究结果表明，发生电偶腐蚀时，铜为阴极，碳钢为阳极。碳钢种类对两者电偶腐蚀的影响较小。通过比较稳态电偶电流密度（i_g^∞）和电偶电压（E_g^∞），发现有氧条件下，随铜/碳钢面积比的增大，对i_g^∞的影响分为三个阶段，分别为：阴极反应电化学控制阶段、O₂扩散控制阶段和阳极反应控制阶段。使用N₂除氧维持的缺氧条件下，随铜/碳钢面积比的增大，i_g^∞值均明显比有氧条件下降低，i_g^∞主要受O₂扩散控制。当铜/碳钢面积比增大到一定值，i_g^∞出现极限值。在手套箱和膨润土泥浆中进行实验时，由于氧含量更低，i_g^∞值进一步降低。有氧条件下，E_g^∞随铜/碳钢面积比的增大正移，表明耦合程度加强；缺氧条件下，E_g^∞随铜/碳钢面积比的增大负移，表明耦合程度减弱。有氧条件下碳钢表面腐蚀产物主要为铁的羟基氧化物，缺氧条件下则为铁的氧化物。

本论文第3章研究了溶液离子浓度变化对T2铜和Q235碳钢电偶腐蚀行为的影响。研究结果表明，在含有Cl⁻和SO₄²⁻的溶液中，随溶液中离子浓度增大，溶解O₂浓度降低，溶液电导率升高，受以上因素的综合影响，i_g^∞先增加后减小，存在最大值。在相同离子浓度的溶液中，随温度升高，溶解O₂含量降低，电导率升高，使得i_g^∞出现最大值时的离子浓度降低。对碳钢表面进行SEM形貌分析发现，在中等离子浓度时，Q235碳钢表面腐蚀程度最严重。

在以上进行的电偶腐蚀实验中，Q235碳钢表面均发现了铜元素的累积。本论文第4章研究了电偶腐蚀过程中铜的迁移机制。通过ICP-MS对溶液中的铜离子含量进行分析，发现缺氧条件下铜离子含量更高。通过络合剂浴铜灵二磺酸二钠盐（BCS）与Cu⁺的特异性反应对溶液中的Cu⁺进行定性检测，发现电偶腐蚀条件下作为阴极的铜也会发生腐蚀溶解并生成Cu⁺，而Cu⁺易被氧化成Cu²⁺，最后沉积到碳钢表面，由于沉积量较少，无法对碳钢表面铜的产物进行定性分析。

综上所述，本论文研究了模拟北山深地质环境下，铜与碳钢电偶腐蚀行为特点及影响因素，为储罐外层破裂后果分析及“双重壁”储罐耐蚀设计的安全评估提供科学依据。

Deep geological disposal is the most reliable method to dispose of high-level nuclear waste at present. This method proposes to seal the nuclear waste in a metal container, wrapped around the container body buffer material, buried in the underground 500 to 1000 meters of disposal. Among them, metal containers are the most important artificial barrier to isolate nuclear waste from human life. After years of investigation, China has selected the Beishan area of Gansu province as the pre-selection site for deep geological disposal, but the material selection and corrosion resistance design of the storage of nuclear waste metal containers are still unresolved, and the design of "double wall" containers with carbon steel (CS) inner liner and Cu outer layer has attracted much attention. When the Cu outer layer is damaged and the Cu and CS are exposed to groundwater at the same time, there is a risk of severe galvanic corrosion of the Cu and CS, which will accelerate the corrosion rate of the CS inner liner. Therefore, the study of galvanic corrosion behavior of Cu and CS in deep geological environment is an important content in the design and safety evaluation of "double wall" containers.

In this paper, the influence of Cu/CS area ratio, temperature, oxygen content and solution ion concentration on the galvanic corrosion current density and galvanic potential of T2 Cu and Q235 CS were studied by simulating the deep geological environment of Beishan area. The surface corrosion products of Q235 CS were analyzed by SEM, EDS, Raman and XPS, and the mechanism and influencing factors of galvanic corrosion between Cu and CS were proposed.

In chapter 2, the influence of Cu/CS area ratio, temperature and oxygen content on the galvanic corrosion behavior of T2 Cu and Q235 CS are studied. The results show that when galvanic corrosion occurs, Cu is the cathode and CS is the anode. The type of CS has little effect on galvanic corrosion. By comparing the steady-state galvanic current density (i_g^∞) and galvanic potential (E_g^∞), it is found that under oxic conditions, with the increase of the Cu/CS area ratio, the influence on i_g^∞ can be divided into three stages: cathode electrochemical control stage, O₂ diffusion control stage and anode reaction control stage. Under anoxic condition maintained by N₂ deaeration, i_g^∞ values are significantly lower than those under oxic conditions with the increase of Cu/CS area ratio, i_g^∞ is mainly controlled by O₂ diffusion. When the Cu/CS area ratio increases to a certain value, a limit value i_g^∞ appears. When the experiment was performed in the glove box and bentonite mud, the i_g^∞ value was further reduced due to the lower oxygen content. Under oxic conditions, E_g^∞ shifts positively with the increase of Cu/CS area ratio, indicating that the coupling degree is strengthened. Under anoxic conditions, E_g^∞ shifted negatively with the increase of Cu/CS area ratio, indicating that the coupling degree weakened. The corrosion products on the surface of CS are mainly iron hydroxyl oxide under oxic conditions and iron oxide under anoxic conditions.

In chapter 3, the influence of the change of ion concentration in solution on the galvanic corrosion behavior of T2 Cu and Q235 CS is studied. The results show that in the solution containing Cl⁻ and SO₄²⁻, the dissolved O₂ concentration decreases and the conductivity of the solution increases with the increase of the ion concentration in solution. Under the comprehensive influence of the above factors, i_g^∞ firstly increases and then decreases, with a maximum value. In a solution with the same ion concentration, the dissolved O₂ content decreases and the conductivity increases with the increase of temperature, so that the ion concentration decreases when the maximum i_g^∞ occurs. SEM analysis on the surface of CS shows that the surface corrosion of Q235 CS is the most serious at the medium plasma concentration.

In the above galvanic corrosion experiments, the accumulation of Cu elements was found on the surface of Q235 CS. In chapter 4, the migration mechanism of Cu during galvanic corrosion is studied. The content of Cu ion in solution was analyzed by ICP-MS, and it was found that the content of Cu ion was higher under anoxic condition.Through the specific reaction of the complexing agent bath copper disodium sulfonate (BCS) with Cu⁺, the Cu⁺ in solution was qualitatively detected. It was found that under galvanic corrosion conditions, Cu as the cathode would also corrode and dissolve and form Cu⁺, and Cu⁺ was easily oxidized into Cu²⁺ and finally deposited on the surface of CS. The products of Cu on the surface of CS cannot be qualitatively analyzed.

In summary, this paper studies the behavior characteristics and influencing factors of galvanic corrosion of Cu and CS under simulated Beishan deep geological environment, which provides a scientific basis for the analysis of the consequences of the rupture of the outer layer of the container and the safety evaluation of the corrosion resistance design of the "double wall" containers.

第1章 绪论 1

1.1 课题研究背景 1

1.2 高放射性核废料深地质处置的国内外研究进展 2

1.2.1 国外研究进展 2

1.2.2 国内研究进展 3

1.3 影响金属储罐腐蚀行为的环境因素 4

1.3.1 温度变化 5

1.3.2 地下水和孔隙水组成 5

1.3.3 氧化还原条件 7

1.3.4 相对湿度 7

1.4 金属储罐材料选择的依据 8

1.4.1 金属储罐失效的定义 8

1.4.2 金属储罐的服役寿命 8

1.4.3 腐蚀和耐蚀材料 8

1.4.4 金属储罐与其他屏障的兼容性 9

1.5 碳钢和铜在深地质环境中的腐蚀行为 9

1.6 深地质环境中影响铜与碳钢电偶腐蚀行为的因素 10

1.7 选题依据及研究内容 11

1.7.1 选题依据 11

1.7.2 研究内容 12

第2章 铜/碳钢面积比、温度和氧含量变化对铜和碳钢电偶腐蚀行为的影响 13

2.1 引言 13

2.2 实验材料与方法 13

2.2.1 实验材料 13

2.2.2 实验试剂 14

2.2.3 实验介质 14

2.2.4 电极的制备 15

2.2.5 电化学实验方法 16

2.2.6 腐蚀产物表面分析方法 18

2.3 结果与讨论 18

2.3.1 不同牌号碳钢对铜和碳钢电偶腐蚀行为的影响 18

2.3.2 温度和氧含量变化对铜和碳钢开路电位的影响 19

2.3.3 温度和氧含量变化对铜和碳钢动电位极化曲线的影响 21

2.3.4 铜/碳钢面积比、温度和氧含量变化对电偶电流密度和电偶电压的影响 23

2.3.5 腐蚀产物表征及腐蚀机理分析 31

2.4 本章小结 35

第3章 模拟液中离子浓度变化对铜和碳钢电偶腐蚀行为的影响 37

3.1 引言 37

3.2 实验材料与方法 37

3.2.1 实验材料 37

3.2.2 实验试剂 37

3.2.3 实验介质 37

3.2.4 电极的制备 38

3.2.5 电化学实验方法 38

3.2.6 腐蚀产物表面分析方法 38

3.2.7 溶液测试方法 38

3.3 结果与讨论 39

3.3.1 Cl−和SO42−浓度变化对铜和碳钢开路电位的影响 39

3.3.2 Cl−和SO42−浓度变化对铜和碳钢动电位极化曲线的影响 41

3.3.3 Cl−浓度变化对铜和碳钢电偶腐蚀行为的影响 43

3.3.4 SO42−浓度变化对铜和碳钢电偶腐蚀行为的影响 46

3.3.5 腐蚀产物表征及腐蚀机理分析 49

3.4 本章小结 53

第4章 碳钢表面铜元素的检测及其迁移规律分析 55

4.1 引言 55

4.2 实验材料与方法 55

4.2.1 实验材料 55

4.2.2 实验试剂 55

4.2.3 实验介质 56

4.2.4 电极的制备 56

4.2.5 电化学实验方法 56

4.2.6 腐蚀产物表面分析方法 56

4.2.7 溶液测试方法 56

4.3 碳钢表面铜元素的检测 56

4.4 溶液中Cu+/Cu2+的检测 60

4.4.1 方法的选择 60

4.4.2 络合剂对电偶腐蚀的影响 61

4.4.3 干扰离子对Cu+检测的影响 62

4.5 铜元素的迁移规律分析 64

4.6 本章小结 64

第5章 结论与展望 67

5.1 主要结论 67

5.2 论文创新点 68

5.3 展望 68

参考文献 71

致谢 79

作者简历及攻读学位期间发表的学术论文与其他相关学术成果 81