摘要
腐蚀电化学噪声是腐蚀系统产生的一种电流、电位随机自发波动的现象。电化学噪声测试技术方法简便,设备简单,对腐蚀体系无外加干扰,已逐渐成为腐蚀研究的重要手段之一,并开始应用于现场腐蚀监测和测试。电化学噪声测试技术已经引起了越来越多研究者的兴趣。
本文研究了油田管道N80钢在NaHCO_3和NaCl溶液中局部腐蚀时产生的电化学噪声,分别研究了实验室单电极和现场探针的点蚀和缝隙腐蚀,并结合金相显微镜和原子力显微镜等技术观察材料表面形貌的变化。本文另一个重点是电化学噪声分析,电化学噪声分析是对电化学噪声测试数据的统计分析过程。本文在电化学噪声分析中,主要采用噪声谱图比较、时域统计分析、频域分析等方法。
在N80钢的点蚀过程,电化学噪声在各个不同点蚀阶段有其特定的噪声峰,因此电化学噪声谱图能够清楚反映出N80钢的亚稳态点蚀、稳态点蚀前期及稳态点蚀后期等不同阶段。噪声峰的出现频率和幅值与侵蚀离子Cl~-浓度有关,Cl~-浓度越大,噪声的频率和幅值越大。当Cl~-浓度超过一临界值后,N80钢从钝化状态快速转变为稳态点蚀,噪声谱图上几乎没有亚稳态特征峰出现。在钝化时间一致的前提下,一小时内产生的亚稳态的点蚀个数与Cl~-浓度成指数函数关系。
电化学噪声电阻R_n值在点蚀各个阶段有明显的变化。尤其是在稳态点蚀后期当宏观蚀点出现后,R_n值会与之前有数量级上的变化。所以,R_n可以用来判断点蚀的不同过程。
缝隙腐蚀研究的初步结果表明:缝隙腐蚀腐蚀发生后,腐蚀电流会在短时间内发生一个很大的波动。
Corrosion electrochemical noise (ECN) is the spontaneous and stochastic fluctuations of current or potential in corrosion system. Electrochemical noise technique is simple and convenient. The equipment of electrochemical noise technique is simple. It doesn’t bring extra disturbance to the corrosion system. It becomes an important technique to study corrosion, it also be used in the industrial field recently. More and more researchers were attracted by the electrochemical noise technique.
Electrochemical noise of the localized corrosion of N80 steel in the NaHCO3 + NaCl solution was studied in this paper. The electrochemical features of pitting corrosion and crevice corrosion were studied by electrochemical noise technique using the experimental electrode and probe. Atomic force microscope and metallographic microscope were also used to study the surface of the electrode. Electrochemical noise analysis was another key point of ECN research. Electrochemical noise analysis was the analysis process of the ECN using mathematic and statistical tools. ECN curves comparing、time domain statistics analysis and frequency domain analysis were used in electrochemical noise analysis in this paper.
Every process of the pitting corrosion of N80 steel had characterized ECN peaks. The different processes of pitting corrosion were identified clearly from these characterized peaks. The ECN peaks were dependent on the concentration of Cl~-. The magnitude and number of the fluctuations increased with the concentration of Cl~-. The characterized ECN peaks of metastable pitting can hardly be found when the concentration of Cl~- exceeded the critical value, the corrosion of N80 steel almost directly changed to the stable pitting after the passivation. After the same time of passivation, the number of metastable pitting peaks in one hour and the concentration of Cl~- had exponential function relation.
Noise resistance (R_n) changed distinctly in the different processes of pitting corrosion, especially before and after the macroscopical pit appeared. R_n can be used to judge the different processes of the pitting corrosion.
In the crevice corrosion, it was found that a huge fluctuation of the corrosion current appeared after crevice corrosion happened.
引文
[1] Bertocci U, Huet F. Noise analysis applied to electrochemical system. Corrosion, 1995, 15(2): 131～144
[2] 张鉴清, 张昭, 王建明等. 电化学噪声的分析与应用-Ⅰ.电化学分析原理. 中国腐蚀与防护学报, 2001, 21(5): 310～317
[3] Magaino S I, Kawaguchi A, Hirata A, et al. Spectrum analysis of corrosion potential fluctuations for localized corrosion of type 304 stainless steel. J. Electrochem. Soc., 1987, 134(12): 2993～2997
[4] Legat A, Doleoek V. Corrosion monitoring system based on measurement and analysis of electrochemical noise. Corrosion, 1995, 51(4): 295～300
[5] Robere P R. Analysis of electrochemical noise by the stochastic process detector method. Corrosion, 1994, 50(7): 502～512
[6] 刘晓方, 王汉功, 权高峰等. 电化学系统噪声分析进展. 腐蚀科学与防护技术, 2001, 13(2): 100～105
[7] Iversion W P. Transient voltage changes produced in corroding metals and alloys. J. Electrochem. Soc., 1968, 115(6): 617～624
[8] Hladky K. Corrosion monitoring. US, A, 4575678, 1983. 1～43
[9] Eden D A, John D G, Darson J L. Localized corrosion monitoring. US, A, 5139627, 1987. 1～21
[10] Darson J L, Eden D A, Carr R N. Method and apparatus for producing electrochemical impedance spectra. US, A, 5425867, 1992. 1～35
[11] Uruchurtu J C, Dawson J L. Noise analysis of pure aluminum under different pitting conditions. Corrosion, 1987, 43(1): 19～25
[12] Isaac J W, Hebert K U. Electrochemical current noise on aluminum microelectrode. J. Electrochem. Soc., 1999, 146(2): 502～509
[13] Legat A, Dolecek V. Corrosion monitoring system based on measurement andanalysis of electrochemical noise. Corrosion, 1995, 51(4): 295～300
[14] 王秉均, 孙学军, 王少勇等. 现代通信系统原理. 第 1 版. 天津: 天津大学出版社, 1999: 30～48
[15] 林海潮, 曹楚南. 孔蚀过程的电化学噪声研究. 中国腐蚀与防护学报, 1986, 6(2): 141～148
[16] Chen J F. Electrochemical emission spectroscopy for monitoring uniform and localized corrosion. Corrosion, 1996, 52(10): 753～785
[17] Cheng Y F, Luo J L, Wilmott M. Spectral analysis of electrochemical noise with different transient shapes. Electochimica Acta, 2000, 45(11): 1763～1771
[18] Hashimoto M, Miyajima S, Murata T. A stochastic analysis of potential fluctuation during passive film breakdown and repair on iron. Corrosion Science, 1992, 33(6): 905～910
[19] Pistorius P C, Burstein G T. Growth of corrosion pits on stainless steel in chloride solution containing dilute sulphate. Corrosion Science, 1991, 33(12): 1885～1897
[20] 曹楚南, 常晓元, 林海潮. 孔蚀过程的电化学噪声特征. 中国腐蚀与防护学报, 1989, 9(1): 21～28
[21] Cheng Y F, Wilmott M, Luo J L. Analysis of the role of electrode capacitance on the initiation of pit for A516 carbon steel by electrochemical noise measurement. Corrosion Science, 1999, 41(6): 1245～1256
[22] Bertocci U, Gabrielli C, Huet F, et al. Noise resistance applied to corrosion measurements Ⅱ.Experimental tests. J. Electrochem. Soc., 1997, 144(1): 37～43
[23] 冯哲圣, 陈金菊, 卢云等. 高纯铝在含 Cl-溶液中电化学噪声的小波包子带能量特征. 中国腐蚀与防护学报, 2003, 23(4): 221～224
[24] 高志明, 宋小平, 庞兴收等. 小波分析在腐蚀电化学瞬间检测中的应用. 中国腐蚀与防护学报, 2001, 21(4): 245～249
[25] Cheng Y F, Luo J L. Passivity and pitting of carbon steel in chromate solution. Electrochimica Acta, 1999, 44(26): 4795～4804
[26] Mansfeld F, Xiao H. Electrochemical noise analysis of iron exposed to NaClsolutions of different corrosivity. J. Electrochem. Soc., 1993, 140(8): 2205～2209
[27] Puget Y, Trethewey K, Wood R J K. Electrochemical noise analysis of polyurethane-coated steel subjected to erosion-corrosion. Wear, 1999, 233/235: 552～567
[28] Gusmano G P, Montesperelli G, Pacetti S, et al. Electrochemical noise resistance as a tool for corrosion rate predication. Corrosion, 1997, 53(11): 860～868
[29] Gabrieli C, Keddam M. Review of application of impedance and noise analysis to uniform and localized corrosion. Corrosion, 1992, 48(10): 794～811
[30] 阎鸿森, 王新凤, 田惠生. 信号和线性系统. 第 2 版. 西安: 西安交通大学出版社, 1998. 3～67
[31] Searson P C, Dawson J L. Analysis of electrochemical noise generated by corroding electrode under open-circuit conditions. J. Electrochem. Soc., 1998, 135(8): 1908～1915
[32] Burg J P. The relationship between maximum entropy spectra and maximum likelihood spectra. Geophysics, 1972, 37(2): 375～376
[33] Lacoss R T. Data adaptive spectral analysis methods. Geophysics, 1971, 36: 661～675
[34] 董泽华, 郭兴蓬, 郑家燊. 电化学噪声的分析方法. 材料保护, 2001, 34(7): 20～23
[35] 丁红波, 夏保云, 潘忠孝等. 电化学噪声数据小波分析法研究. 电化学, 2000, 6(2): 238～243
[36] Joseph B, Dai X D, Motard R L, et al. Improved discrimination of electrochemical noise signals using wavelet analysis. Corrosion, 2001, 57(5): 394～403
[37] 高志明, 李井会, 高礼让等. 小波分析在化学中的应用进展. 化学进展, 2000, 12(2): 179～191
[38] Hoar T P, Jacob W R. Breakdown of passivity of stainless steel by halide ions. Nature, 1967, 216(5121): 1299～1301
[39] Heusler K E, Fischer L. Kinetics of pit ignition at the alloy Fe5Cr. Werkstoffe undcorrosion, 1976, 27(10): 698～701
[40] Okada T. A theoretical analysis of the electrochemical noise during the induction period of pitting corrosion in passive metals Part I. J. Electroanal. Chem., 1991, 297(2): 349～359
[41] Macdonald D D, Sikora E, Sikora J. The kinetics of growth of the passive film on tungsten in acidic phosphate solutions. Electrochimica Acta, 1998, 43(19-20): 2851～2861
[42] Okada T. A theoretical analysis of the electrochemical noise during the induction period of pitting corrosion in passive metals Part II. J. Electroanal. Chem., 1991, 297(2): 361～375
[43] MacFarlane D R, Smedley S J. The dissolution mechanism of iron in chloride solutions. J. Electrochem. Soc., 1986, 133(10): 2240～2253
[44] Shibata T. Stochastic studies of passivity breakdown. Corrosion Science, 1990, 31(3): 413～423
[45] Naschstedt K, Heusler K E. Electrochemical noise at passive iron. Electrochimica Acta, 1988, 33(3): 311～321
[46] Williams D E, Westcott C. Studies of the ignition of pitting corrosion on stainless steels. J. Electroanal. Chem. Interfacial Electrochem., 1984, 180(1-2): 549～564
[47] 崔思贤. 石化工业中金属材料的腐蚀与防护(2). 石油化工腐蚀与防护, 1995, 17(1): 47～50
[48] Evans U R. 金属的腐蚀与氧化. 第 1 版. 华保定译. 北京: 机械工业出版社, 1976. 152～170
[49] 关宝印. 钢质管道的腐蚀控制技术(二)-腐蚀与检测. 管道技术与设备, 1994, 13(2): 33～36
[50] Pickering H W, Frankenthal R P. On the mechanism of localized corrosion of iron and stainless EM-1, 2. J. Electrochem. Soc., 1972, 119(10): 1297～1310
[51] Newman R C, Isaacs H S, Alman B. Effects of sulfur compounds on the pitting behavior of type 304 stainless steel in near-neutral chloride solution. Corrosion, 1982, 38(5): 261～265
[52] Frankel G S, Stockert L, Hunkeler F, et al. Metastable pitting of stainless steel. Corrosion, 1987, 43(7): 429～436
[53] Oldfield J W, Sutton W H. Crevice corrosion of stainless steels EM-2.Experimental studies. Br. Corros. J., 1978, 13(1): 13～22
[54] Srihar N, Dunn D S. Effect of applied potential on changes in solution chemistry inside crevices on type 304L stainless and alloy 825. Corrosion, 1994, 50(11): 857～872
[55] 司利平. 输油管道的防垢与防腐. 化学清洗, 1998, 14(6): 25～28
[56] 张爱社, 吝爱芳. 中原油田油系统腐蚀状况分析及对策. 石油与天然气化工, 2002, 31(1): 41～43
[57] 郑国汉. 腐蚀与防护技术新近展. 四川化工与腐蚀控制, 2002, 1(5): 29～32
[58] Salaita G N, Moran J P, Stoner G E. Localized corrosion behavior of alloy 2090-the role of microstuctural heterogeneity. Corrosion, 1990, 46(8): 610～617
[59] 梁成浩. 钛的缝隙腐蚀行为研究. 稀有金属材料与工程, 1994, 23(6): 41～45
[60] 梁成浩. 工业纯 Al 的缝隙腐蚀再钝化电位. 金属学报, 1994, 30(4): 165～168
[61] Kim J G, Buchanan R A. 氯化物溶液中铝铁中间化合物的点蚀与缝隙腐蚀. 石油化工腐蚀与防护, 1995, 14(4): 38～42
[62] Valentini C R, Moina C A, Vilche J R, et al. Electrochemical behavior of iron in stagnant and stirred potassium carbonate-bicarbonate solution in the 0-75 degree temperature range. Corrosion Science, 1985, 25(11): 985～997
[63] 陆大. 随机过程及应用. 第 1 版. 北京:清华大学出版社, 1986. 324～376
[64] 陈良均, 朱庆棠. 随机过程及应用. 第 1 版. 北京:高等教育出版社, 2003. 182～241
[65] 邱于兵, 黄家怿, 郭兴蓬. 多项式拟合法消除电化学噪声的直流漂移. 华中科技大学学报(自然科学版), 2005, 33(10): 39～45
[66] 张昭, 张鉴清, 李劲风等. 因次分析法在电化学噪声分析中的应用. 物理化学学报, 2001, 17(7): 651～654
[67] Li F B, Thompson G E, Newman R C. Force modulation atomic force microscopy:background, development and application to electrodeposited cerium oxide films. Applied Surface Science, 1998, 126 (1-2): 21～33