碳钢在红沿河海洋工业大气环境中的初期腐蚀行为

The Initial Corrosion Behavior of Carbon Steel Exposed to the Coastal-Industrial Atmosphere in Hongyanhe

利用腐蚀失重、SEM、XRD、红外光谱、电化学方法对碳钢在红沿河海洋工业大气环境中的初期腐蚀行为进行研究。结果表明,碳钢在该环境中的初期腐蚀动力学符合线性规律,腐蚀速率呈现波动变化。腐蚀产物的成分在早期阶段主要为γ-FeOOH和α-FeOOH,随后出现了一定含量的Fe3O4,γ-FeOOH的含量随着时间呈现减小趋势,而α-FeOOH的变化相反。碳钢腐蚀10 d后的表面主要为点蚀和不规则局部腐蚀形貌,点蚀区的形貌因具体微环境的差异而不同。腐蚀60 d后的材料表面基本覆盖了腐蚀产物,但是锈层厚度不均匀,而且表面有很多巢结构,这种结构不仅容易聚集污染物而且有利于传质过程的进行,减弱了锈层的保护作用。结合电化学测试结果,进一步讨论了腐蚀产物层的保护作用。

The atmospheric corrosion of carbon steel is an extensive topic that has been studied by many authors who have proposed many mechanisms and techniques for studying the phenomena involved and have reported long term exposure data in many different regions throughout the world. However, there are few literatures that have discussed the corrosion results of carbon steel exposed for shortterm time which can contribute to the understanding of the initial corrosion mechanisms. Therefore in this work, mass-loss measurement, SEM, XRD, infrared spectroscopy and electrochemical techniques have been used to investigate the initial corrosion evaluation of carbon steel exposed to a coastal-industrial atmospheric environment in Hongyanhe. Mass-loss results show that the short-term corrosion kinetic of carbon steel is in good fitting with linear function, and the average corrosion rate fluctuates over time and don’t show the downward trend observed in long-term exposure experiments. Lepidocrocite, goethite and magnetite are identified in corrosion products formed on the surface of exposed carbon steel samples.The content of lepidocrocite shows a decreasing trend over exposure time, while goethite is the opposite.Magnetite appears in the later stages and keeps stable in amount. Pitting and an irregular localized corrosion can be observed clearly on the surface of carbon steel specimens exposed for 10 d. The corrosion product at pitting regions is circular flowery shape which varies in details as the physical and chemical environments change. The rust layer grows over time and eventually covers the entire surface of carbon steel samples exposed for more than 60 d, yet its thickness is uneven. The surface of rust layer has many nest-shaped structures that can’t barricade the physical transmission effectively. The protective effect of rust layer has been further discussed in combination with electrochemical results.