IOCAS-IR  > 海洋环境腐蚀与与生物污损重点实验室
海水抽水蓄能电站金属结构腐蚀规律及选材研究
杨丹
Subtype博士
Thesis Advisor黄彦良
2021-05-14
Degree Grantor中国科学院大学
Place of Conferral中国科学院海洋研究所
Degree Name理学博士
Degree Discipline海洋腐蚀与防护
Keyword金属材料 腐蚀产物层 钝化膜 腐蚀规律 选材
Abstract

海水抽水蓄能技术是保障电力系统经济、可靠、安全运行和提高电力工业经济效益的一种新型抽水蓄能发电方式,建设海水抽水蓄能电站具有广阔的发展前景。海水抽水蓄能电站运行工况苛刻,以海水直接作为介质,海水化学性质活泼,会对电站金属结构造成腐蚀,金属材料在高压水流的作用下会发生更加严重的腐蚀。不同的金属材料在海水中的耐蚀性能不同,金属在海水中存在发生局部腐蚀的可能,如点蚀、缝隙腐蚀、应力腐蚀等。局部腐蚀是影响金属材料强度和使用寿命的主要腐蚀形式,点蚀、缝隙腐蚀、应力腐蚀、腐蚀疲劳等会加速金属的早期破坏、失效,甚至引起重大事故,影响电站的稳定运行,从而增加了工程费用和维护费用,造成极大的经济损失。因此,研究海水抽水蓄能电站金属结构的选材和防腐问题具有重要意义。

基于以上背景,本文以备选材料碳钢、低合金钢、不锈钢、铜合金和纯钛为研究对象,对金属材料在模拟海水抽水蓄能电站运行工况下的腐蚀规律及腐蚀机理进行了研究。具体研究如下:

1)通过电化学测试技术研究了碳钢、低合金钢和不锈钢在常压静止海水中的腐蚀行为。温度影响不锈钢表面钝化膜的性能,随着温度的升高,钝化膜的呈现溶解状态,性能有所下降,但是904L奥氏体不锈钢和2205双相不锈钢形成的钝化膜具有优异的耐蚀性能,在海水中的腐蚀速率极低。提出了海水中温度影响碳钢和不锈钢点蚀的机理模型,即金属的腐蚀与表面氧化膜(钝化膜)的状态有关,当温度升高到某一温度时,表面氧化膜变得活跃,开始溶解;温度继续升高,氧化膜处于局部溶解状态,此时有发生点蚀的倾向;当温度升高到特定值Tc时,金属表面氧化膜完全溶解并消失,此时金属处于均匀腐蚀状态。不锈钢的Tc远远高于碳钢、低合金钢,常温下碳钢已处于活性溶解状态,低温下的碳钢表面氧化膜没有完全溶解,有发生点蚀的倾向。904L奥氏体不锈钢和2205双相不锈钢在海水中具有较宽的钝化区间,恒电位极化结果表明,不锈钢在一定的电位范围内能够维持钝化状态,而当超过某一电位时,钝化膜的性能会大幅度降低,不锈钢钝化膜的性能是钝化膜生成速率与溶解速率共同作用的结果。

2)通过电化学测试技术与SEM研究了静水压力对Q235碳钢、2205双相不锈钢的影响。随着压力的升高,Q235碳钢在整个浸泡周期的自腐蚀电位负移,阳极溶解加速,但是碳钢的自腐蚀电流密度没有较大差异。通过计算经验点蚀电位Eb100与自腐蚀电位的差值评价碳钢点蚀倾向,发现在浸泡初期,压力会影响金属点蚀行为,对浸泡前期的金属采用恒电位极化和SEM分析,结果表明压力升高,碳钢的点蚀倾向增加。循环极化曲线结果也表明碳钢在4 MPa海水浸泡后期发生了点蚀。压力升高,2205双相不锈钢表面钝化膜的性能下降。

3)通过电化学测试、SEMXRDEDSXPSFTIR和拉曼光谱研究了碳钢、低合金钢和不锈钢在模拟电站静水压力为4MPa的环境中的腐蚀行为。Q235碳钢、X70管线钢和Q345低合金钢腐蚀产物膜的成分相同,对金属起到一定的保护作用,锈层表面后期会出现裂纹,金属/腐蚀产物界面会发生点蚀并自催化加速腐蚀,循环极化曲线结果也表明碳钢表面发生了点蚀。不锈钢在高压环境中的腐蚀行为与其表面钝化膜的性能有关,钝化膜的性能与钝化膜的生成速率和溶解速率有关,随着浸泡时间的增加,904L奥氏体不锈钢钝化膜性能略有升高,但基本处于稳定状态。2205双相不锈钢随着压力作用时间的增加,钝化膜厚度增加,性能升高。后期Cl-富集在钝化膜表面,钝化膜处于溶解状态,性能降低,但不锈钢仍处于钝化状态,没有发生点蚀。

(4) 通过电化学测试、SEMXRDEDSXPSFTIR和拉曼光谱研究了碳钢、低合金钢和不锈钢在模拟电站静水压力为4MPa的流动环境中的腐蚀行为。流速加剧了Q235碳钢、X70管线钢和Q345低合金钢的腐蚀,流动海水对金属早期形成的腐蚀产物有物理剥离作用,持续新鲜的金属表面阳极溶解过程加速,腐蚀速率升高。流动海水不会使整个腐蚀产物膜都剥落,所以浸泡早期,在金属/腐蚀产物界面诱发点蚀。而且锈层在压力、流速的共同作用下,更快出现了裂纹,也加速了点蚀发生,循环极化曲线测试结果也证实碳钢在更早的时间发生了点蚀。流动环境下,金属表面生成的腐蚀产物膜变厚,但是保护作用并没有得到增强,金属基体表面出现了更加密集的点蚀坑,局部腐蚀更加严重。流速也影响了不锈钢表面钝化膜的形成,流动海水对表面钝化膜有物理冲刷减薄作用,与静止环境相比,钝化膜性能下降。虽然流动海水在一定的流速下会促进钝化膜的生成,但是不锈钢钝化膜在此实验流速下处于持续溶解状态,钝化膜性能随着水流作用时间的增加而降低。

(5) 通过电化学测试、SEMXRD研究了铜合金、纯钛在模拟电站换热器温度下的腐蚀行为。铜及铜合金在海水中生成具有保护作用的氧化膜,且氧化膜随着浸泡时间的延长厚度增加,保护作用增强,铜及铜合金在模拟换热器温度下的腐蚀电流密度都不高。紫铜和锡黄铜在模拟换热器温度下发生了局部腐蚀,锡黄铜发生脱锌腐蚀。铜镍合金在模拟换热器温度下以均匀腐蚀为主,生成的氧化膜结构会随着浸泡时间的延长变得疏松,Cl-影响铜镍合金表面氧化膜的性能,使其后期转化为保护作用弱的铜绿。纯钛TA2在模拟换热器温度下基本不腐蚀,钝化性能优异。

6本文通过研究备选金属材料在模拟海水抽水蓄能电站运行工况下的腐蚀行为,并根据前期的文献调研为海水抽水蓄能电站金属结构提供选材思路。电站的输水压力管道建议X70管线钢,海水冷却系统换热器建议钛材TA2,,进/出水口闸门门叶建议Q235碳钢,拦污栅建议不锈钢或铜合金材料,电站的尾水隧洞建议钢筋混凝土,小型海水管道建议不锈钢材料,处于苛刻环境的部位建议双相不锈钢。

Other Abstract

Seawater pumped storage power is a new type of pumped storage power generation to ensure the economic, reliable and safe operation of power system. It can also improve the economic benefits of power industry. The construction of seawater pumped storage power station has broad development prospects. Station use seawater directly as the medium and the operation conditions of station are harsh. Therefore, metal structures will suffer from severe normal corrosion and localized corrosion in high-pressure flowing seawater. Metal materials have different corrosion resistance in seawater. And localized corrosion is the main form of corrosion that affects the strength and service life of metal materials. Pitting corrosion, crevice corrosion, stress corrosion, corrosion fatigue, and so on will accelerate the early damage and failure of metal, which will even cause major accidents and affect the stable operation of power station. Materials failure caused by localized corrosion increases the engineering cost and maintenance cost, leading to great economic losses. Therefore, it is of great significance to study the metal materials selection and anti-corrosion of metal structure in seawater pumped storage power station.

Based on the above background, the corrosion laws and corrosion mechanisms of carbon steel, low alloy steel, stainless steel, copper alloy and titanium under simulated corrosion environments of station were studied in this paper. The main results and conclusions are as follows:

(1) The corrosion behavior of carbon steel, low alloy steel and stainless steel in seawater was studied by electrochemical testing technology. Temperature affects the performance of the passive film of stainless steel. With the increase of temperature, the passive film appeared to be dissolved, and the performance of passive film decreased. However, the passive film formed on stainless steel had excellent corrosion resistance so that the corrosion rate of stainless steel was very low. The mechanism model of pitting corrosion of carbon steel and stainless steel under the influence of temperature in seawater was proposed. That is, the corrosion of metal is related to the state of surface oxide film (passive film). When the temperature rises to a certain temperature, the surface oxide film becomes active and begins to dissolve. When the temperature continues to rise, the oxide film is in the state of local dissolution, and there is a tendency of pitting at this time. When the temperature rises to a certain value TC, the oxide film on the metal surface completely dissolves and disappears, and the metal is in a uniform corrosion state. The TC of stainless steel is much higher than that of carbon steel and low alloy steel. At room temperature, carbon steel is in active dissolution state. The oxide film on carbon steel surface is not completely dissolved, and there is a tendency of pitting corrosion at lower temperature. 904L austenitic stainless steel and 2205 duplex stainless steel have a wide passivation range in seawater. Potentiostatic polarization results showed that stainless steel can maintain a passivation state in a certain potential range. When the potential exceeded a certain value, the performance of passivation film will be greatly reduced.

(2) The effect of hydrostatic pressure on Q235 carbon steel and 2205 duplex stainless steel was studied by electrochemical testing and SEM. With the increase of pressure, the corrosion potential of Q235 carbon steel in the whole immersion cycle shifted negatively. The anodic dissolution accelerated, but the corrosion current density of carbon steel had no significant difference. The pitting tendency of carbon steel was evaluated by calculating the value of Eb100 -Ecorr. It was found that the pressure would affect the pitting behavior at the initial immersion stage. Potentiostatic polarization and SEM results showed that the pitting tendency of carbon steel increased with the increase of pressure. The results of cyclic polarization curves also showed that pitting corrosion occurred in the later stage of 4 MPa seawater immersion. The performance of passive film on 2205 duplex stainless steel decreased with the increase of pressure.

(3) The corrosion behaviors of carbon steel, low alloy steel and stainless steel in simulated power station with hydrostatic pressure of 4MPa were studied by electrochemical test, SEM, XRD, EDS, XPS, FTIR and Raman spectroscopy. The corrosion product film of Q235 carbon steel, X70 pipeline steel and Q345 low alloy played a certain protective role on metal. Cracks appeared on the surface of rust layer later and pitting corrosion occurred at the interface of the metal and corrosion products. The results of cyclic polarization curve also show that pitting corrosion occurred on the surface of carbon steel. The corrosion behavior of stainless steel in high pressure environment was related to the performance of passivation film. The performance of passivation film was depended on the formation rate and dissolution rate of passivation film. With the increase of soaking time, the passivation film performance of 904L stainless steel increased slightly and it was basically stable. The passivation film thickness and performance of 2205 duplex stainless steel increased with the increase of pressure action time. In the later stage, the passivation film was in dissolution state and its performance was reduced. In short, stainless steel was still in passivation state, having no pits.

(4) The corrosion behavior of carbon steel, low alloy steel and stainless steel in the flowing environment of simulated power station hydrostatic pressure of 4MPa was studied by electrochemical testing, SEM, XRD, EDS, XPS, FTIR and Raman spectroscopy. The results showed that the corrosion rate of carbon steel or low alloy steel is aggravated in the flowing seawater. The flowing seawater had physical stripping effect on the corrosion products formed in the early stage. The anodic dissolution process of the continuous fresh metal surface accelerated and the corrosion rate increased. In the early stage of immersion, pitting corrosion was induced at the interface of metal and corrosion product. Moreover, the rust layer cracks occurred more quickly in the flowing seawater, which also accelerated the occurrence of pitting corrosion. The result of cyclic polarization curve confirmed that pitting corrosion occurred earlier. Under the flowing environment, more intensive pitting pits appeared on the surface of the metal substrate, and the local corrosion was more serious. The flow velocity also affected the formation of passive film on the stainless steel surface. The flowing seawater has physical scouring and thinning effect on the surface of passive film. Compared with the static environment, the performance of passive film decreased. Although the flowing seawater can promote the formation of passive film at a certain flow rate, the passive film of stainless steel was in a state of continuous dissolution at this experimental flow rate. And the performance of passive film decreases with the increase of water flow action time.

(5) The corrosion behavior of copper alloy and pure titanium at simulated heat exchanger temperature was studied by electrochemical test, SEM and XRD. The corrosion current density of copper or copper alloy at simulated heat exchanger temperature was not high. Local corrosion of copper and tin brass occurred at simulated heat exchanger temperature. And dezincification corrosion of tin brass occurred. The results showed that the corrosion of Cu-Ni alloy was mainly uniform at the simulated heat exchanger temperature. The oxide film structure will become loose with the prolongation of immersion time. Cl- affected the performance of the oxide film on the surface of Cu-Ni alloy, which makes it turn into the weak protective green in the later stage. Titanium TA2 has excellent passivation performance and no corrosion at simulated heat exchanger temperature.

(6) In this paper, the corrosion behavior of alternative metal materials under simulated operation conditions of seawater pumped storage power station is studied. And according to the previous literature research, the idea of material selection for metal structure of seawater pumped storage power station is provided. X70 pipeline steel is recommended for the water delivery pressure pipeline of the power station. TA2 is recommended for the heat exchanger of the seawater cooling system. Q235 carbon steel is recommended for the gate leaf of the inlet / outlet gate. Stainless steel or copper alloy is recommended for the trash rack. Reinforced concrete is recommended for the tailrace tunnel of the power station. Stainless steel is recommended for the small seawater pipeline, and duplex stainless steel is recommended for the structures in harsh environment.

Subject Area海洋科学其他学科
MOST Discipline Catalogue理学::海洋科学
Pages150
Funding ProjectNational Key R&D Program of China[2017YFB0903702] ; National Key R&D Program of China[2017YFB0903700] ; National Key R&D Program of China[2017YFB0903700] ; National Key R&D Program of China[2017YFB0903702]
Language中文
Table of Contents

1 绪论... 1

1.1 引言... 1

1.2 海水腐蚀... 2

1.2.1 海水腐蚀类型... 3

1.2.2 海水腐蚀的影响因素... 7

1.2.3 苛刻海洋环境腐蚀研究现状... 9

1.3 常用金属及其海水腐蚀特征... 11

1.3.1 碳钢和低合金钢... 11

1.3.2 不锈钢... 12

1.3.3 铜与铜合金... 12

1.3.4 钛与钛合金... 13

1.4 海水抽水蓄能电站的关键金属结构及备选材料... 14

1.4.1 进出水口闸门... 14

1.4.2 拦污栅... 15

1.4.3 输水管道... 15

1.4.4 水泵/水轮机... 16

1.4.5 换热器... 16

1.5 研究目标及研究内容... 17

1.5.1 研究目标... 17

1.5.2 研究内容... 18

2 备选材料在常压静止海水中的腐蚀规律研究... 19

2.1 引言... 19

2.2 实验方法... 19

2.2.1 试样制备和腐蚀介质... 19

2.2.2 实验装置... 21

2.2.3 电化学测试... 21

2.3 结果与讨论... 22

2.3.1 碳钢和低合金钢在常压静止海水中的腐蚀规律... 22

2.3.2 904L奥氏体不锈钢在常压静止海水中的腐蚀规律... 26

2.3.3 2205双相不锈钢在常压静止海水中的耐蚀性能... 31

2.3.4 点蚀机理分析... 35

2.4 本章小结... 36

3 备选材料在高压静止海水中的腐蚀行为研究... 37

3.1 引言... 37

3.2 实验方法... 37

3.2.1 试样制备和腐蚀介质... 37

3.2.2 高压水环境腐蚀试验... 37

3.2.3 电化学测试... 38

3.2.4 形貌观察和腐蚀产物分析... 38

3.3 结果与讨论... 39

3.3.1 Q235碳钢在高压静止海水中的腐蚀行为... 39

3.3.2 X70管线钢在高压静止海水中的腐蚀行为... 47

3.3.3 Q345低合金钢在高压静止海水中的腐蚀行为... 55

3.3.4 不锈钢在高压静止海水中的腐蚀行为... 62

3.3.5 静水压力对局部腐蚀的影响及腐蚀机理分析... 69

3.4 本章小结... 75

4 备选材料在高压流动海水中的腐蚀行为研究... 77

4.1 引言... 77

4.2 实验方法... 77

4.2.1 试样制备和腐蚀介质... 77

4.2.2 高压流动水环境腐蚀试验... 77

4.2.3 电化学测试... 78

4.2.4 形貌观察和腐蚀产物分析... 78

4.3 结果与讨论... 78

4.3.1 Q235碳钢在高压流动海水中的腐蚀行为... 78

4.3.2 X70管线钢在高压流动海水中的腐蚀行为... 86

4.3.3 Q345低合金钢在高压流动海水中的腐蚀行为... 93

4.3.4 不锈钢在高压流动海水中的腐蚀行为... 100

4.3.5 流速对金属腐蚀的影响... 106

4.4 本章小结... 107

5 备选材料在模拟换热器冷却水温度下的腐蚀行为研究... 109

5.1 引言... 109

5.2 实验方法... 111

5.2.1 试样制备和腐蚀介质... 111

5.2.2 模拟换热器腐蚀环境试验... 112

5.2.3 电化学测试... 112

5.2.4 形貌观察和腐蚀产物分析... 112

5.3 结果与讨论... 112

5.3.1 紫铜在模拟换热器冷却水温度下的腐蚀行为... 112

5.3.2 锡黄铜在模拟换热器冷却水温度下的腐蚀行为... 119

5.3.3 铜镍合金在模拟换热器冷却水温度下的腐蚀行为... 124

5.3.4 纯钛TA2在模拟换热器冷却水温度下的腐蚀行为... 128

5.3.5 合金成分对铜合金在海水中耐蚀性能的影响... 128

5.4 本章小结... 129

6 结论与展望... 131

6.1 结论... 131

6.2 创新点... 133

6.3 展望... 134

参考文献... 135

... 145

作者简历及攻读学位期间发表的学术论文与研究成果    147

Document Type学位论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/170564
Collection海洋环境腐蚀与与生物污损重点实验室
Recommended Citation
GB/T 7714
杨丹. 海水抽水蓄能电站金属结构腐蚀规律及选材研究[D]. 中国科学院海洋研究所. 中国科学院大学,2021.
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