【作者】 姜文军；

【导师】 郭兴蓬；

【作者基本信息】 华中科技大学 ， 应用化学， 2006， 硕士

【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NaHCO₃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。更多还原

【Abstract】 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.更多还原