【作者】 赵霞；

【导师】 王佳；

【作者基本信息】 中国海洋大学 ， 海洋化学工程与技术， 2007， 博士

【摘要】 有机涂层是一种延缓金属腐蚀的最有效和最经济的材料之一,金属的腐蚀与有机涂层的性能密切相关,而涂层防腐蚀性能取决于涂层与金属基体之间的粘结强度和涂层对水及其它侵蚀性粒子的抗渗透能力等诸多因素。本论文主要采用电化学方法并结合人工神经网络方法研究了干湿循环和全浸泡这两个最为常见自然环境条件下的涂层/金属在腐蚀介质中的失效规律。本文的主要研究工作包括:(1)首先,采用电化学方法研究了全浸泡过程中醇酸铁红涂层失效过程中的腐蚀行为。研究了涂层/金属电极开路电位随时间的变化规律。腐蚀电位在浸泡初期均出现明显的负移趋势,说明水分子能够迅速到达基底金属表面,但是随着浸泡时间的延长,腐蚀电位正移,最后稳定在一个较稳定的数值。研究了阻抗模型随浸泡时间的变化,在浸泡初期,40μm涂层/金属体系阻抗未呈现纯电容特性,随着时间的延长阻抗谱时间常数增多,在浸泡后期阻抗谱中出现了扩散阻抗,该扩散阻抗并非典型Warburg阻抗。对于较厚的60μm涂层/金属电极体系,浸泡初期阻抗谱能够表现为纯电容特性。采用四种阻抗模型对EIS数据进行了拟和。不同厚度的涂层在相近的腐蚀阶段呈现相同的腐蚀模型。并通过Cc, Rc, Cdl和Rct随浸泡时间的变化表征了涂层/金属体系的腐蚀行为。从logF-|Z|图中选取了一个新的特征参数,对于两种不同厚度涂层的失效过程均能与阻抗谱进行较好的对应。该方法不需要受其他条件的限制,只要做出logf-|Z|图,就能对涂层吸水、破坏以及涂层下金属腐蚀进行一个全面判断。综合上述所有参数的变化规律,绘制了涂层失效过程与多参数变化示意图。(2)采用电化学方法研究了干湿循环条件下,涂层/金属电极的腐蚀行为。研究了40μm厚度涂层在干湿循环条件下失效过程的阻抗谱特征变化情况。根据干湿交替阻抗谱的变化特征,将涂层的状态分为亚稳态,过渡态和稳态,并且分别研究了这三个状态下涂层的阻抗谱特征,建立了等效电路模型,解析了Cc, Rc, Cdl, Rct四个主要的电化学参数,与全浸泡条件下的参数进行了一一对比,找到了两者的相关性。(3)采用自组织人工神经网络的方法,以Bode图中的阻抗变化率参数为输入样本进行训练学习,研究了干湿循环和全浸泡两种条件下的涂层失效过程。研究发现,对于两种条件下的涂层失效过程的研究结果,采用人工神经网络方法和采用电化学方法所得到的结果基本一致。因此,自组织人工神经网络方法可以作为一种很好的辅助阻抗谱研究涂层失效过程的工具。更多还原

【Abstract】 Organic coating is one kind of the most effective and most economic materials to prevent the metal from damage. The metallic corrosion is closely relative with the ability of organic coating. The anticorrosion ability of coating is determined by the bond strength and anti-penetration ability to water and other eroding ions. This dissertation chiefly adopts electrochemical impedance spectroscopy (EIS) method combine with artificial neural network(ANN) to study the deterioration rule of coating under wet-dry conditions and immersion state. The main work of this paper including:(1) Corrosion behaviour of iron oxide red alkyd (IORA) primer is researched at the immersion state by EIS method.The changing rule of OCP on time is researched. OCP moves to negative value at the early immersion stage which indicates that water molecule has reached metal surface.Evolution of impedance model as immersing time is studied. At the early stage of immersion, pure capacitance characteristic is not presented in EIS plot of 40μm coating/metal system. Time constant of EIS increases as time prolonging and diffusion impedance appears at late stage of immersion. But for 60μm coating system, EIS can show pure capacitance characteristic at the early stage.Four kinds of impedance models are adopted to fit EIS plot. The same rule of corrosion model exists in the similar corrosion stage of different thickness coating. And the corrosion behaviour of coating/metal system is characterized by the changing trend of Cc, Rc, Cdl and Rct on time.A new characteristic parameter is selected from logf- |Z| plot which shows a good correspondence with EIS and coating picture for two different thickness coatings. This method will not be limited by other conditions provided logf-|Z| plot is made. According to changing rules of all parameters above, a comprehensive map is drawn to signify coating deterioration process.(2) Electrochemical method is adopted to research the corrosion behaviour of coating under wet-dry conditions.Under wet-dry conditions, the changing rule of EIS for 40μm coating is researched. According to characteristic of EIS under wet-dry conditions, coating state can be divided into three states which are metastable state, transition state and stable state. The characteristics of EIS under these three states are studied, and then equivalent circuit model is established, the parameters- Cc, Rc, Cdl and Rct are analyzed comparing with those at the immersion state.(3) Self-organization map (SOM) artificial neural-network is adopted. The parameter of changing rate of impedance gained from bode plot is regarded as the import sample for training and studying. Coating deterioration process of wet-dry conditions and immersion state are researched by this method. The same results can be gained by EIS method and SOM network, which proves that SOM method can be used as a good assisted tool to research the deterioration process of organic coatings.更多还原