摘 要
2205双相不锈钢广泛应用于海洋工程、船舶、化工、轮轴等领域，然而在使用过程中可能发生腐蚀失效，导致工程安全事故的发生。因此，研究2205双相不锈钢的钝化膜微区电化学行为及其稳定性具有重要的理论和应用价值。本文通过扫描电子显微镜、原位傅里叶变换红外光谱和电化学阻抗谱等技术对2205双相不锈钢表面钝化膜的微区结构和阻抗特性进行了研究。结果表明，钝化膜包含Cr（OH）3、FeCrO4、Fe（OH）3和Cr2O3等物质，其中Fe（OH）3和Cr（OH）3在钝化过程中起到了重要作用。钝化膜的电化学阻抗谱呈现出一条特征的直线段，其斜率则表征了表面阻抗。此外，本文还探讨了钝化膜在不同电位下的微区电化学行为及钝化膜的稳定性问题。研究表明，钝化膜的稳定性受到溶液中氧气的影响，随着氧气浓度的降低，钝化膜的稳定性逐渐降低。
关 键 词：2205双相不锈钢，钝化膜，微区电化学行为，电化学阻抗谱。
Abstract
2205 duplex stainless steel is widely used in marine engineering, ships, chemical industry, axles and other fields. However, corrosion failure may occur during use, leading to engineering safety accidents. Therefore, it is of great theoretical and practical value to study the micro-electrochemical behavior and stability of passivation film on 2205 duplex stainless steel. In this paper, the surface microstructure and impedance characteristics of passivation film on 2205 duplex stainless steel were studied by scanning electron microscopy, in situ Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy. The results show that the passivation film contains substances such as Cr(OH)3, FeCrO4, Fe(OH)3 and Cr2O3, among which Fe(OH)3 and Cr(OH)3 play important roles in the passivation process. The electrochemical impedance spectroscopy of the passivation film shows a characteristic straight line segment, and the slope of the straight line segment reflects the surface impedance. In addition, the micro-electrochemical behavior of the passivation film at different potentials and the stability of the passivation film were also explored. The study shows that the stability of the passivation film is affected by the oxygen content in the solution. With the decrease of oxygen concentration, the stability of the passivation film gradually decreases.
Keywords: 2205 duplex stainless steel, passivation film, micro-electrochemical behavior, electrochemical impedance spectroscopy
The micro-electrochemical behavior of the passivation film on the surface of 2205 duplex stainless steel was investigated using electrochemical impedance spectroscopy (EIS) technique. The experiment was conducted in a 3.5% NaCl solution at various potentials ranging from -0.5 V to +1.5 V vs. SCE. The results show that the formation of the passivation film on the surface of 2205 duplex stainless steel is a complex process that involves several electrochemical reactions.
At potentials more negative than -0.1 V vs. SCE, the passivation film undergoes dissolution due to the reduction of the oxygen dissolved in the solution. As the potential is increased to 0.3 V vs. SCE, the formation of the passivation film begins to occur through the oxidation of the iron atoms on the surface of the steel. At potentials between 0.5 V and 1.5 V vs. SCE, the passivation film becomes more stable due to the formation of a thicker and denser oxide layer.
The stability of the passivation film was also found to be influenced by the oxygen content in the solution. As the oxygen concentration decreases, the stability of the passivation film also decreases. This is because the oxygen dissolved in the solution plays an important role in the formation and maintenance of the passivation film.
In conclusion, the micro-electrochemical behavior of the passivation film on the surface of 2205 duplex stainless steel has been studied using EIS technique. The results show that the formation and stability of the passivation film are influenced by several factors including the potential, the oxygen content in the solution, and the composition of the steel. The findings of this study provide insights into the mechanisms of passivation and corrosion resistance of duplex stainless steels in aggressive environments
Furthermore, the study also highlights the importance of surface treatment and polishing in enhancing the passivation and corrosion resistance of duplex stainless steel. It was observed that the chemical composition and morphology of the passive film were significantly affected by the polishing method used prior to the electrochemical measurements.
Another important aspect that affects the passivation behavior of duplex stainless steel is the presence of impurities and contaminants on the surface. Inadequate cleaning of the steel surface can lead to the formation of a less stable and less protective passive layer, thereby reducing the corrosion resistance of the material. Therefore, proper surface cleaning and preparation are crucial in maintaining the optimum corrosion protection of duplex stainless steel.
In terms of the electrochemical processes involved in the passivation of duplex stainless steel, it has been shown that the formation of the passive film is controlled by the reduction of dissolved oxygen at the metal surface. This reduction reaction facilitates the formation of a dense and protective oxide layer on the steel surface, which acts as a barrier against further corrosion.
Furthermore, the electrochemical behavior of the passive film can be characterized by its impedance response. EIS measurements reveal that the passive film exhibits a high resistance to charge transfer, indicating its insulating nature. The impedance data also pr
不锈钢钝化ovide information about the thickness and quality of the passive film, which can be used to evaluate the corrosion resistance of duplex stainless steel in different environments.
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