无氧铜在北方地区生活用水中腐蚀行为的研究

发布时间：2018-04-29 02:42

  本文选题：无氧铜 + 腐蚀行为　； 参考：《深圳大学》2017年硕士论文

【摘要】：本文以材质为无氧铜的燃气热水器近几年来在我国北方地区使用几个月就漏水失效为背景,采用循环伏安法与Tafel曲线分析探究了无氧铜在含有C1~-、SO_4~(2-)和CO_3~(2-)的生活用水中的腐蚀行为,通过XRD、SEM及金相显微镜观察分析经模拟浸泡腐蚀试验后的铜管表面形貌与腐蚀产物,来研究换热器的温度与工况对铜腐蚀行为的影响。研究讨论结果如下:1)在国家生活卫生用水标准GB5749-2006的规定范围内C1~-、SO_4~(2-)和CO_3~(2-)对无氧铜都有侵蚀性,C1~-与SO_4~(2-)的侵蚀性最强。C1~-的浓度增加会加速铜全面腐蚀,会促进铜的点蚀形核,但不利于点蚀的发展;SO_4~(2-)的浓度增加对铜的全面腐蚀影响并不大,易引起点蚀;CO_3~(2-)浓度的增加可加速铜的全面腐蚀;CO_3~(2-)在低于0.01 mol/L时,浓度的增加易引发点蚀,而在CO_3~(2-)浓度大于0.03 mol/L时,浓度的增加会抑制点蚀。2)在 C1~-与 SO_4~(2-)混合体系中,C1~-浓度对铜的全面腐蚀起着主导作用,C1~-浓度的增加会促进铜的全面腐蚀;当C1~-的浓度低于0.005 mol/L时,SO_4~(2-)的增加会大大增强铜的点蚀倾向,引起点蚀的发生;当C1~-浓度大于0.03 mol/L时,C1~-浓度将对铜点蚀行为起主导作用。在C1~-与CO_3~(2-)混合体系和SO_4~(2-)与CO_3~(2-)混合体系中,当溶液中CO_3~(2-)浓度小于0.01 mol/L时,C1~-或SO_4~(2-)的增加会加速铜的全面腐蚀,促进铜点蚀的发生;而当溶液中CO_3~(2-)浓度大于0.03 mol/L时,溶液中铜的腐蚀腐蚀行为主要由CO_3~(2-)浓度来控制,CO_3~(2-)浓度的增加会抑制铜点蚀的发生。3)在20~50℃范围内,温度的上升会加速铜的全面腐蚀,促进铜表面的点蚀形核,但是会抑制点蚀的发展。北方地区的生活用水虽达到了GB5749-2006的要求,但是由于其SO_4~(2-)含量较高,所以会使无氧铜有很大的点蚀倾向,易引发点蚀。4)无氧铜在流水条件下的腐蚀要比静水条件下的严重。无氧铜在温度为30℃时腐蚀较为严重,易发生点蚀;30℃条件下无氧铜表面因均匀腐蚀所形成的腐蚀产物层脆弱保护性差,易于被击穿,形成大阴极小阳极的腐蚀电池而引发点蚀。5)晶粒尺寸对无氧铜的腐蚀行为的影响不大;表面裂纹的存在会加快铜的全面腐蚀与增大其点蚀敏感性;水质对无氧铜腐蚀性的影响要大于表面裂纹的影响。6)热交换器的失效原因为盘管发生点蚀穿孔。热交换器盘管上点蚀孔分布在温度为30℃的区域,这与模拟腐蚀浸泡实验所得出无氧铜在温度为30℃时易发生点蚀的结论相一致。7)影响无氧铜腐蚀行为的两个主要因素是水质与均匀腐蚀所形成的腐蚀产物层;无氧铜的均匀腐蚀与点蚀会同时进行,均匀腐蚀的腐蚀产物层不均匀与缺陷的存在都会促进点蚀的发生。同时水质中含有较高的SO_4~(2-)时;会大大提高无氧铜的点蚀敏感性,进一步促进无氧铜发生点蚀。
[Abstract]:In this paper, based on the leakage failure of gas water heaters made of oxygen free copper in the north of China in recent years, the corrosion behavior of oxygen free copper in domestic water containing C _ (1) -C _ (so _ 4) and CO _ (3) is investigated by cyclic voltammetry and Tafel curve analysis. The surface morphology and corrosion products of copper tube after simulated immersion corrosion test were observed and analyzed by XRDX SEM and metallographic microscope to study the effect of heat exchanger temperature and working condition on copper corrosion behavior. The results of the study are as follows: (1) within the scope of the National Standard for domestic Sanitary Water (GB5749-2006), the concentration of C _ (1) and C _ (1) (2) and COSP _ (2) are both corrosive to oxygen-free copper (and so _ (4) ~ (2) the concentration of the most corrosive copper,. C _ (1) ~ (-), will accelerate the overall corrosion of copper and will promote the pitting nucleation of copper. However, the increase in the concentration of so _ 4 / T _ 2) does not have a great effect on the overall corrosion of copper. The increase in the concentration of COT _ 3 / T _ 2-can accelerate the overall corrosion of copper. () when the concentration is lower than 0. 01 mol/L, the increase of the concentration will easily lead to pitting corrosion. When the concentration of CO _ 3O _ 2 is greater than 0.03 mol/L, the increase of concentration will inhibit the pitting corrosion. 2) in the mixed system of C _ (1) and S _ (4) O _ (2), the concentration of C _ (1) ~ (-) plays a leading role in the overall corrosion of copper. The increase of concentration of C _ (1) ~ (-) can promote the overall corrosion of copper. When the concentration of C1O- is lower than 0.005 mol/L, the increase of the concentration of so _ 4 ~ + _ 2) will greatly enhance the pitting corrosion tendency of copper and cause the occurrence of pitting corrosion, and when the concentration of C _ (1) ~ (-) is greater than 0.03 mol/L, the concentration of C _ (1) ~ (-) will play a leading role in the pitting corrosion behavior of copper. In the C _ 1 / C _ 3 / C _ T _ 2 / C _ _ _ The corrosion behavior of copper in the solution is mainly controlled by the concentration of COSP _ 3 ~ (2). The increase of the concentration of CO _ 3 / C _ (2) will inhibit the occurrence of copper pitting corrosion. 3) in the range of 20 ~ 50 鈩，

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