ETA对核电站二回路镍合金690和碳钢的腐蚀影响

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	ETA对核电站二回路镍合金690和碳钢的腐蚀影响
	孙荣鹏
学位类型	硕士
导师	韩恩厚
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	腐蚀科学与防护
关键词	碳钢 690合金腐蚀乙醇胺（eta）二回路水化学 Carbon Steel Alloy 690 Corrosion Ethanolamine (Eta) Secondary Side Water Chemistry
摘要	"我国采用的是压水堆核电（PWR）技术，使用水作为冷却剂。在高温环境下，难以避免会产生材料的腐蚀问题，而良好的水化学有助于缓解核电站中材料的腐蚀，保证核电站的安全和盈利。现行的压水堆核电站二回路中开始采用全可挥发性水化学处理技术，乙醇胺（ETA）作为pH控制剂具有很多优点，但关于ETA对二回路中材料的腐蚀影响却少有研究，本文研究了不同浓度ETA对690合金和碳钢的腐蚀影响，为确定合理的添加浓度提供了实验基础。不同ETA浓度下的浸泡实验结果表明，ETA对690合金腐蚀影响不明显，XPS结果没有观察到双层膜结构，但在一些样品中观察到了Cr的富集峰。浸泡实验发现提高ETA浓度对碳钢的点蚀抑制明显，根据点缺陷模型（PDM）分析，pH的增加能减少金属基体与氧化膜之间的金属离子空位的浓度，减少金属离子空位源，抑制点蚀的形成。常温电化学实验发现ETA浓度对690合金腐蚀的影响很小，随着ETA浓度的增加，阻抗谱的容抗弧减小，电子传递电阻增大。常温时，ETA浓度为40ppm，60ppm，80ppm时，碳钢的极化曲线相似，存在钝化区，与ETA浓度为20ppm时有很大的差异，阻抗谱分析表明20ppm，40ppm，60ppmETA浓度下阻抗谱相似，80ppm ETA浓度的阻抗谱容抗弧减小。常温40ppm ETA溶液中三种氯离子浓度下690合金的极化行为相似，添加氯离子使690合金的抗腐蚀能力减弱，腐蚀电流密度增大。而且随着氯离子浓度的增加，阻抗谱的容抗弧减小。80ppm ETA溶液中三种氯离子浓度下690合金的极化行为相似，极化曲线的参数相近。氯离子的添加使腐蚀反应更加容易进行，但80ppm ETA在某种程度上抑制了氯离子的有害作用。在常温40ppm ETA溶液中，不添加氯离子和添加1ppm氯离子时碳钢的极化曲线基本重合，都有钝化区间，添加10ppm氯离子时，钝化区间消失。在80ppmETA浓度下，三种氯离子浓度下碳钢的极化行为相似，都有钝化区间，电流密度也相似。 280℃时690合金在20ppm，40ppm，60ppmETA溶液中的极化行为相似，电流随电位逐渐增加直到达到一个平台，之后电流基本不再随电位增加而增加。但在70ppm，80ppm ETA 浓度下，690合金出现了钝化区，之后690合金的电流密度随着电位一直保持着增长的趋势。极化曲线及其曲线参数表明60ppm是ETA影响690合金极化行为高低浓度的分界线。 280℃时20ppm、40ppm、60ppmETA溶液中碳钢的极化曲线也相似，阳极电流随着电位增加而存在一个平台。而当ETA浓度增加到70ppm，80ppm时，极化曲线出现明显的差异。ETA浓度达到60ppm及以上时，腐蚀电流密度减小明显，对极化曲线及其参数的分析表明对碳钢而言，60ppm 是ETA高低浓度的分界线，ETA浓度在分界线上下碳钢的极化行为差异明显。"
其他摘要	"With rapidly developing economy in our country, urbanization and industrialization is pushing forward, needs for electricity increases quickly. According to electricity need prediction, calculated by medium increase rate, our country’s electricity need will increase 3 times in 25 years from 2015 to 2040.It is obvious that to meet such a enormous electricity it is necessary to develop new alternate energy. While nuclear power plant is the only mature technology which can provide cheap continuous electricity with large amount, it certainly will be developed widely. Our country adopts pressurized water reactor(PWR) technology which uses water as coolant. In high temperature environment it is unavoidable to have some corrosion problems, while good water chemistry is helpful to allay material corrosion and to assure safety and profitability of nuclear power plant. Nowadays secondary water chemistry in PWR is using all volatile treatment technology, Ethanolamine(ETA) using as pH control agent has many advantages, but research about its corrosion effects on secondary side material is little, so in this dissertation the effect of ETA concentration on secondary side material carbon steel and alloy 690 is studied to provide some experimental evidence for determining the appropriate adding concentration. Experimental results in different ETA concentration show effects of ETA on alloy 690 is not obvious, and the double layer has not been observed in its oxide, but some enrichment peak of Cr in some sample. In immersion experiments it is discovered that increasing ETA concentration will significantly inhibit pitting in carbon steel. According to Point Defect Model(PDM)analysis, increase in pH will reduce the metal ion vacancy concentration between metal and oxide and inhibit the reaction between oxide and solution which will generate metal ion vacancy, thus the formation of pitting of carbon steel will be inhibited. In electrochemical experiment at ambient temperature it is found that ETA concentration has little influence on corrosion of alloy690, the EIS curve diminishes and the charge transfer resistance increases as the ETA concentration increases. At ambient temperature when ETA concentration is 40ppm, 60ppm, 80ppm, polarization curves of carbon steel are similar, there is passivation in these curve, which is quite different from polarization curve in 20ppm ETA solution. EIS in 20ppm,40ppm, 60ppm ETA solution is similar, while EIS curve in 80ppm diminishes. Polarization curve of alloy 690 in three different chloride concentration in 40ppm ETA solution at ambient temperature is similar, the chloride ion decreases corrosion resistance of alloy 690 and the corrosion current increases as the chloride ion concentration increases. EIS of alloy 690 in three different chloride ion concentration is separated, and as the chloride ion concentration increases the EIS curve diminishes. Polarization curve of alloy 690 in three different chloride concentration in 80ppm ETA solution at ambient temperature is very similar, parameters of polarization curve in three different chloride ion concentration is close. Chloride ion makes corrosion easier but 80ppm ETA counteract its bad influence to some extent. In 40ppm ETA concentration polarization curve of carbon steel with non-chloride ion and with 1ppm chloride ion is nearly the same and there is passivation, while with 10ppm chloride ion the passivation is gone. Polarization curve of carbon steel in three different chloride ion concentrations in 80ppm ETA solution is similar, there is passivation and the current density is close, EIS shows the same result. At 280℃ polarization of alloy 690 in 20ppm,40ppm,60ppm ETA concentration is similar, the current increases as the potential increases until reaches a plateau. But there is passivation of alloy 690 in70ppm, 80ppm ETA solutions, and the current is keeping increasing as the potential increases. Polarization curve and its parameters indicate 60ppm is the watershed of ETA concentration for alloy 690. At 280℃ polarization of carbon steel in 20ppm,40ppm,60ppm ETA concentration is similar, the current reaches a plateau as the potential increases. When ETA concentration increased to 70ppm,80ppm, polarization curve is quite different from 20ppm,40ppm,60ppm, and there is no current plateau, which indicate as the potential increases the protection of whole oxide becomes weak. As ETA concentration reaches 60ppm and above corrosion current decreases obviously, polarization curve and its parameters indicate 60ppm is the watershed of ETA concentration for carbon steel."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64529
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	孙荣鹏. ETA对核电站二回路镍合金690和碳钢的腐蚀影响[D]. 北京. 中国科学院金属研究所,2012.