Kelvin探头振动电容法技术在大气腐蚀中的应用

介绍了Kelvin探头振动电容法在腐蚀中的应用原理及试验装置,Kelvin探头(也称为振动电容法)技术应用到金属腐蚀的研究中,可以在不需与被测试样表面相接触的条件下,用Kelvin探针作参比电极,测量液膜下金属的腐蚀速率,电极电位及极化曲线.     

扫描Kelvin探针表面电位特征参数在有机涂层劣化研究中的应用

为了研究扫描Kelvin探针表面电位技术在有机涂层劣化研究中的应用并选择合理的评价特征参数,结合使用电化学阻抗谱EIS和扫描Kelvin探针(SKP)技术研究了有机涂层在3.5%NaCl溶液中的劣化过程,分析了有机涂层劣化过程中扫描Kelvin探针表面电位分布数特征参数Vmin、Vmax-Vmin的变化规律,并首次提出了表面电位梯度最大值gradmax这个特征参数。结果证明,扫描Kelvin探针特征参数gradmax、Vmin,Vmax-Vmin和电化学阻抗谱具有很好的相关性,扫描Kelvin探针特征参数能够很好地用来评价有机涂层劣化,表面电位梯度最大值gradmax可以用来研究有机涂层下金属腐蚀发生的趋势和速度。     

利用Kelvin探针进行金属薄液层下电化学测量

利用线性回归法测Kelvin电位装置对铜,锌及碳钢进行了阴极极化曲线测试和腐蚀电位随相对湿度变化的监测结果表明阴极极限电流密度随液膜厚度的减小而增大金属腐蚀电位随相对湿度增加而下降.     

Kelvin探针测量技术在电化学研究中的应用进展

    Kelvin探针测量技术被引入到腐蚀研究领域后,成为研究薄液膜和有机涂层下金属腐蚀的有力电化学工具和手段.Kelvin探针技术与原子力显微镜技术相结合产生出扫描Kelvin探针力显微镜,使Kelvin技术在材料研究和腐蚀领域得到了更好的应用.本文简述了Kelvin 探针技术的测量原理和装置,重点综述了近十年来该技术在电化学研究中的应用进展.     

Q235钢/NaCl液滴界面微区电化学特征参数分布特征

本文采用扫描Kelvin探针、扫描振动电极等方法表征了NaCl液滴覆盖下Q235钢表面的微区电化学参数分布的特征.结果证实,NaCl液滴下碳钢表面的电位分布和电流密度分布是不均匀的,中心为阳极区,边缘为阴极区.液滴中心和边缘阴阳极电位相差0.4 V,阴阳极电流密度相差0.9μA/cm2.NaCl液滴下碳钢表面电化学参数的不均匀分布导致液滴边缘发生强烈的阴极极化,导致附近区域碱性化是微液滴形成的主要原因.     

气相环境中无机盐微粒沉积金属表面的电位分布

使用扫描Kelvin探头参比电极技术研究了气相环境中无机盐微粒沉积诱发金属腐蚀过程的电位分布特征．结果表明。金属电位分布的变化与无机盐的种类和环境相对湿度有密切关系．在较低相对湿度下，无机盐的沉积不会改变金属表面均匀的电位分布；在较高相对湿度下，沉积无机盐位置的电位首先会形成电位深谷，然后深谷周围区域的电位逐渐升高，形成火山型不均匀电位分布．Na2SO4、NaCl和KCl等无机盐在Zn和钢表面沉积均可观察到这种电位分布的变化．无机盐的沉积诱发的不均匀电位分布在金属表面形成了阴极区和阳极区，构成了腐蚀原电池，从而开始了大气腐蚀过程．     

用Kelvin探头技术研究铝合金的大气腐蚀

选择航空工业广泛使用的铝、铝合金及其涂层的试样，利用自行研制的Kelvin探头大气腐蚀测定仪、扫描电镜等设备，研究了纯铝试样随温、湿度变化，其表面电位的变化规律，测定了铝合金及涂层试样大气曝晒试验和周浸试验前后的表面电位、形貌,对铝、铝合金以及涂层的腐蚀规律进行了初步的探讨.结果表明，纯铝试样表面无可见液膜时，腐蚀电位随相对湿度增加逐渐下降；表面有可见液膜时，随着液层蒸发逐渐减薄，电位逐渐正移.铝合金裸材在北京大气环境下电位变化较小，且各个位置的电位基本相同.带涂层的试样优先在缺陷处发生腐蚀，并不断向周围扩展，涂层的剥离面积不断增大.涂层的铝合金，划痕处在腐蚀发生的初期腐蚀电位向负方向变化很快，但是随着时间的延长，腐蚀电位变化的速率减慢，并有向正方向移动的趋势.      

腐蚀电化学多参数相关法研究有机涂层失效子过程特征

同步采用电化学阻抗和腐蚀电位等平均信息方法以及Kelvin探针电位分布信息方法研究了有机涂层失效过程特征及其相关性.研究发现,有机涂层失效过程的电化学阻抗、腐蚀电位、电位分布等特征和腐蚀电动势数据具有腐蚀相关性,其对应有机涂层失效子过程均具有特征响应.与单一参数分析相比,多参数相关分析方法能够同时从多个不同角度识别和评价涂层失效过程的进展,能够获得涂层失效各个子过程进程的更深入的信息.     

应用Kelvin探针研究不锈钢焊接区的耐蚀性

用扫描Kelvin探针技术测定了不锈钢焊接接头的形貌和伏打电位差分布,发现此电位分布图与焊接区在尿素合成介质中长期腐蚀后的形貌有良好的对应关系     

Kelvin探头参比电极技术在大气腐蚀研究中的应用

Kelvin探头参比电极技术是近年来大气腐蚀领域中最为活跃的研究方向之一．它能够不接触、无破坏的检测薄液膜甚至涂层下金属表面的腐蚀电位分布，文中介绍了该技术的发展历史、技术要点，着重讨论了该技术在研究金属表面有机涂层的剥离和薄液层下金属的腐蚀两方面的应用。     

Studies in the Electrical Double Layer at Metal/Polymer Interfaces by Scanning Capacitive Probe

A scanning capacitive probe (the Kelvin probe) is applied to studying metal/polymer contacts. Potential drop across the electrical double layer of oriented ionic dipoles at the metal/polymer interface was shown to mainly contribute to measured Volta potentials. Amino groups of epoxy coatings are protonated upon their interaction with hydroxylated metal surfaces; being positively charged, they reduce the Volta potential of the metals. Acid groups of alkyd coatings acquire a negative charge and increase the Volta potentials of the metals. Polyaniline (an electron-conducting polymer) accepts metal's electrons to its Fermi level, thus producing a Schottky barrier. In this case, the potential at the contact does not depend on the metal nature; it approaches the aniline intrinsic redox-potential.     

使用Kelvin探头参比电极技术进行薄液层下电化学测量

研究了Ｋｅｌｖｉｎ探头参比电极技术测定薄液层下金属电化学行为的方法。为改善Ｋｅｌｖｉｎ探头装置的测试性能，采取和若干提高信噪比的措施，如采用压陶瓷振动驱动器和测量交流信号的电压成分等。实验结果表明，改进的这套装置可用于测试极薄液层下的金属电极电位，电位随时间的变化，腐蚀电位分布及极化曲线等稳态电化学行为，是研究大气腐蚀过程的有效工具之一。     

大气腐蚀电化学研究方法现状

综述了大气腐蚀的电化学研究方法，尤其是薄液膜下 的电化学交流阻抗(EIS)和Kelvin探针技术的应用，比较了不同方法的优缺点.EIS比较适合 于研究薄液膜下金属的腐蚀历程；Kelvin探头适合于研究金属表面的局部腐蚀.最后展望了 大气腐蚀的研究趋势.     

Characterization of corrosion of X65 pipeline steel under disbonded coating by scanning Kelvin probe

Corrosion of X65 pipeline steel under a disbonded coating was studied by scanning Kelvin probe measurements. Three types of specimen were designed and prepared to investigate the effects of immersion time, oxygen concentration and wet-dry cycle on Kelvin potential profile and thus corrosion behavior of the steel. Kelvin potential measured on “intact” area is shifted negatively with time, indicating an increasing water uptake under the “intact” coating. With the increase of the amount of solution, it is expected that the electrolyte concentration and electrochemical reaction rate change, resulting in a significant decrease of interfacial potential. Moreover, there is a more negative Kelvin potential on disbonded area than that on “intact” area. The negative shift of Kelvin potential is attributed to corrosion reaction of steel occurring under the disbonded coating. Due to the narrow geometry of coating disbondment, an oxygen concentration difference exists along the depth of the disbondment. The corrosion behavior under disbonded coating strongly depends on the oxygen partial pressure and local geometry. With continuous purging of nitrogen and removing of oxygen, Kelvin potential tends to be identical throughout the disbonded area. During wet-dry cycle, the thickness of solution layer trapped under disbonded coating decreases due to evaporation of water. With the decrease of solution layer thickness, the measured Kelvin potential decreases, indicating that the effect associated with the reduction of oxygen solubility in the concentrated solution during drying of electrolyte is favored over that related to the enhanced oxygen diffusion and reduction. There exists a critical thickness of solution layer, below which the oxygen solubility is sufficiently low to support the electrochemical corrosion reaction of steel.     

Heterogeneous electrochemical characteristics of biofilm/metal interface and local electrochemical techniques used for this purpose

Biofilms on metal surface in an aqueous environment is a complex electrochemical system. The heterogeneous electrochemical characteristics of biofilm/metal interface and local electrochemical techniques used for this purpose are discussed in this work. The techniques presented in this work include microelectrode, scanning vibrating electrode, the wire beam electrode method, and scanning electrochemical microscopy. Two potentially useful techniques, localized electrochemical impedance spectroscopy and scanning Kelvin probe force microscopy, are also discussed. The advantages and limitations of these techniques are summarized. A new approach: numerical simulation of micro‐electrochemical heterogeneity of biofilm covered metals is introduced.     

Potential control under thin aqueous layers using a Kelvin Probe

Kelvin Probes can be modified to control as well as monitor potential. The design and operation of two different Kelvin Probe Potentiostats (KPPs) are described in this paper. One approach uses a permanent magnet and double coil to oscillate the needle at a fixed frequency, an AC backing potential, and software analysis and control schemes. This technique can also control the distance between the tip and sample, thereby tracking the topography of the sample. Both KPPs were used to make measurements on Type 304L stainless steel under thin layers of electrolyte. Cathodic polarization curves exhibited a limiting current density associated with oxygen reduction. The limiting current density varied with solution layer thickness over a finite range of thickness. Anodic polarization curves on 304L in a thin layer of chloride solution resulted in pitting corrosion. The breakdown potential did not vary with solution layer thickness. However, the thin layer was observed to increase in volume remarkably during pit growth owing to the absorption of water from the high humidity environment into the layer with ionic strength increased by the pit dissolution. The open circuit potential (OCP) and solution layer thickness were monitored during drying out of a thin electrolyte layer. Pitting corrosion initiated, as indicated by a sharp drop in the OCP, as the solution thinned and increased in concentration.