【作者】 刘杰；

【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， 2011， 博士

【摘要】 随着陆地矿产资源被过度消耗,世界各国都把目光投向如何开采和利用深海中的矿产资源。有机涂层是深海环境中对海洋工程结构防护的最重要手段之一。深海压力会加速有机涂层的失效,也是导致海洋船舶、石油平台、深潜器等损坏的原因之一。因此,对于深海环境中金属的腐蚀行为和有机涂层失效机制的研究已成为当前各国腐蚀科研人员极为关注的问题。本文主要以模拟深海压力环境为实验背景,采用电化学方法以及物理测试技术研究了低合金钢在不同海水压力下的腐蚀电化学行为及微观形貌,又研究了完好和不同破损程度的有机涂层在模拟深海压力下的劣化过程。采用电化学阻抗谱（EIS）技术测试了电极的阻抗响应随浸泡时间的变化,据此建立相应的等效电路模型,并根据等效电路对各阻抗谱进行解析。同时,将丝束电极（WBE）技术和电化学阻抗谱（EIS）技术联用研究了常压海水浸泡条件下有机涂层的劣化过程。取得主要研究进展和成果如下:（1）首先,研究了低合金钢在不同海水压力下的腐蚀电化学行为及微观形貌。结果表明,随着海水压力的增大,两种钢均发生严重的腐蚀。深海压力加速了两种低合金钢的阳极溶解速度。两种钢均由低压下的均匀腐蚀变为高压下的局部腐蚀,但腐蚀形貌有较大差异。高压下的X钢出现明显的“浅碟状”腐蚀坑,而高压下的Y钢出现了明显的隧道形腐蚀坑。研究了2.5MPa的海水压力下水在涂层中的传输行为。结果表明,浸泡初期水在涂层中的传输行为符合Fick扩散定律。与常压下水的传输行为区别在于,海水压力加速了水向涂层内渗入,缩短了涂层达到吸水饱和状态所需要的时间,进而导致涂层在吸水饱和状态持续时间缩短。涂层提前达到耐压极限的时间即为“突变点”在lnC_c t^0.5曲线出现的时间。此后,涂层电容急剧增大,涂层完全失效。研究了2.5MPa的海水压力下人工破损涂层的EIS响应特征。结果表明,在相同破损率和相同浸泡时间条件下,海水压力下涂层的阻抗值明显比常压下涂层的要小,同时随浸泡时间延长,试样的涂层电容呈增加趋势,极化电阻不断减小。高压海水使水等侵蚀性物质更易从破损处向涂层内部渗透,导致涂层与基体附着力降低,从而加速涂层失效。另外,总结了腐蚀产物在破损处的生成与堆积对不同压力下破损涂层腐蚀进程的影响。研究了海水交变压力下有机涂层的劣化过程。结果表明,海水交变压力加速了有机涂层的失效,其主要原因是交变压力下水对涂层的渗透和逆渗透加速了涂层从基体金属上的剥离。（2）结合WBE和EIS技术对涂层劣化的研究发现,阳极电流在电极表面的长期存在说明电极表面的涂层存在缺陷,从而导致金属发生严重腐蚀。涂层下的电极均会发生电流极性转换现象。涂层丝束电极的总阻抗谱响应主要反映的是局部涂层缺陷最为严重处的电极过程特征,而其它区域的涂层劣化过程和涂层下基体金属的腐蚀反应过程信息均被掩盖。丝束电极（WBE）技术和电化学阻抗谱（EIS）技术联用能够更为详尽地研究涂层的局部劣化过程以及准确提供涂层微区缺陷处金属基体的腐蚀反应过程信息。更多还原

【Abstract】 With the excessive consumption of land resources, more and more efforts are being devoted to exploit marine resources in the world. Organic coating is one of the most important methods to protect ocean engineering structures in deep-sea environment. The pressure of seawater could accelerate the deterioration process of organic coating, and it may lead to the damage of ships, oil platforms and submersible boats. Therefore, the research of corrosion behaviors of metal and the deterioration mechanism of organic coating is being paid attention to. This dissertation based on the experiment of simulated deep-sea environment. Corrosion electrochemical behaviors and morphology of low alloy steels under different pressure of seawater were investigated by various electrochemical methods and physical testing technologies. The deterioration processes of intact coatings and the coatings with artificial defect and water transport behaviors in coatings under different pressure were investigated. The evolutions of impedance of coating with immersion time were measured by electrochemical impedance spectroscopy （EIS）, and electrical equivalent circuits （EEC） corresponding to the different immersion stages were established. The EIS data of coating/metal systems were fitted to suitable EECs. The deterioration processes of coatings under atmospheric pressure of seawater were studied using the wire beam electrode （WBE） method and electrochemical impedance spectroscopy （EIS）. The main results and progresses of this work are outlined as following:（1） The corrosion electrochemical behaviors and morphology of low alloy steels under different pressure of seawater were investigated. The results showed that with the increase of hydrostatic pressure of seawater, the corrosion resistance of X steel and Y steel were deteriorated, which were attributable to the increase of the anodic reaction rates. And the morphology of two steel changed significantly and differently. Under high pressure of seawater, some shallow-dish shape localized corrosion appeared on the surface of X steel, whereas on the surface of Y steel some tunnel localized corrosion appeared.The water transport behavior in the organic coating immersed under 2.5MPa pressure of seawater was investigated. The results suggested that the water transport behavior followed the Fick diffusion laws during the initial period of immersion. Contrast to the water transport behavior under atmospheric pressure, the time that the water uptake of the coating kept a saturation state has been shorten. The“turning point”appeared in the lnC_c t^0.5 curve when the pressure critical value of coating has been reached. Subsequently, the coating capacitance sharply increased and the coating was complete failure.The EIS response characteristic of the deterioration process of organic coating under 2.5MPa pressure of seawater was studied. The results demonstrated that the impedance of coating with artificial defects at 2.5 MPa pressure decreased faster than that under atmospheric pressure, and with the increase of immersion time, the capacitance of the samples increased, and the resistance decreased at 2.5 MPa pressure, indicating that high sea pressure greatly accelerated the degradation of organic coating. Moreover, the effect of accumulation of corrosion products at defect location of coating to the corrosion process of coating with artificial defect under different pressure was investigated.The deterioration processes of organic coating under alternating pressure of seawater were investigated. The results showed that the deterioration process of organic coating has been accelerated under alternating pressure of seawater, and the reason is that the permeation and reversed-permeation of seawater into the coating accelerated the delamination of coating from the substrate metal.（2） The current distribution results of the WBE showed that the substrate metal were corroded seriously because the high anode current appeared in the interface in a long time. And there were the phenomena of polarity transition of current on the coating/steel interface. During the entire coating deterioration process, the EIS characteristics were dominated by the substrate corrosion process of the most serious defect, and the coatings and underlying corrosion process were“averaged”out. Through the combination of the WBE and EIS, the local deterioration of the coating and corrosion process of the substrate metal could be exactly detected.更多还原