涂层防护体系加速腐蚀失效机制研究

发布时间：2018-01-04 17:40

本文关键词：涂层防护体系加速腐蚀失效机制研究　出处：《北京化工大学》2015年硕士论文　论文类型：学位论文

【摘要】：有机涂层体系的广泛使用不可避免的引起腐蚀失效的发生并造成极大危害。如果能够尽可能的对复杂大气环境腐蚀下有机涂层体系做出较为真实的模拟并对其的失效做出较为全面、准确的评价,知道其失效机制并采取有效措施将会大大减少腐蚀危害的发生与发展。基于以上问题,研究金属涂层防护体系的腐蚀失效并为制定相关防腐蚀措施的标准提供重要依据就显得尤为重要。本课题展开了对有机涂层防护体系加速腐蚀失效的研究。首先,利用层次分析法(AHP)建立涂层防护体系的综合评价模型；其次,通过电化学数据对此评价模型进行了验证,并利用其对涂层体系的失效结果进行评价；最后,通过一些现代仪器分析方法对有机涂层防护体系在光化学与腐蚀介质协同作用下的腐蚀失效机制进行了研究。研究结果表明：综合评价模型对涂层体系的失效程度能够较好的评价,并且权重系数范围界定使其有了更高的适应性；电化学方法得到的涂层电阻对评分结果的检验证实了涂层评价模型的正确性。通过SEM观察发现涂层体系经过8个周期加速腐蚀实验后其表面确实发生了鼓泡与裂纹,甚至截面出现剥离：通过EDS分析,发现腐蚀后涂层的Cl-增多,C/O显著减小,腐蚀越严重这种趋势更明显；在截面上,Cl-随着腐蚀介质的渗入深度而逐渐减少。而填料二氧化钛也随着涂层中有效成分的破坏而逐渐流失。利用FITR分析可知三种有机涂层腐蚀失效过程具有相同的腐蚀机理,且树脂链断裂均表现为N-H键的断裂和C-O键断裂。因此,可以推断,涂层中有效成分在光化学作用下遭到破坏,加速了氯离子等腐蚀介质在涂层中渗入进而使涂层发生鼓泡,开裂和剥落等腐蚀失效现象。而涂层中的成膜物质聚氨酯通过改性以及涂层中二氧化钛的添加会大大改善涂层体系的耐蚀性能。表面只有超音速火焰喷涂处理的无涂层涂层体系在经过四个周期加速实验就发生严重腐蚀,通过XPS分析知,实验前涂层体系的涂层表面无Fe元素存在而腐蚀后的有铁元素且以FeO、Fe3O4、 Fe2O3、FeOOH、Fe2(SO4)3五种氧化物的形式存在：腐蚀不严重部位二价铁的含量比腐蚀严重部位多,而Fe2(SO4)3在腐蚀严重部位含量多,则铁的转化过程可能是从稳定的Fe单质和二价铁氧化物,中间经过三价铁的氧化物,最后形成硫酸铁：超音速火焰喷涂层的失效也表现出C/O元素含量比在腐蚀发生后会变小,而其主要喷涂物质WC可能以其氧化物的形态离开涂层,使其对基体金属的保护作用逐渐失去,基体金属则不断遭受腐蚀介质的腐蚀而破坏。
[Abstract]:Organic coatings are widely used will inevitably cause corrosion failure occurred and caused great harm. If possible corrosion of the complex atmospheric environment simulation system to make the organic coating more real and made more comprehensive on the failure of the accurate evaluation, know the failure mechanism and take effective measures will greatly reduce the occurrence and development of corrosion damage. Based on the above problems, the corrosion protection system of metal coating failure and corrosion protection measures for the formulation of relevant standards important basis is particularly important. This thesis researches on accelerating the corrosion of organic coating protection system. First, using the analytic hierarchy process (AHP) to establish comprehensive evaluation system for protective coating secondly, through the electrochemical data model; this evaluation model is verified, and the use of coating failure results For evaluation; finally, through some modern instrumental analysis methods to study the organic coating corrosion protection system of collaborative under photochemical and corrosion failure mechanism. The results show that the comprehensive evaluation model of the coating system can evaluate the degree of failure, and the weight coefficient scope makes it have higher adaptability; test of coating resistance electrochemical method on the score results confirmed the correctness of the coating evaluation model. Observed by SEM coating system after 8 cycles of accelerated corrosion test on the surface after the really happened bubble and crack, even stripping section: through EDS analysis, it is found that the corrosion coating of Cl- C/O was significantly increased. The more serious corrosion decreases, this trend is more obvious; in cross section, Cl- decreased with the depth of penetration of corrosive medium and titanium dioxide with filler. The active ingredient in the coating damage gradually lost. The corrosion mechanism of the same with using the FITR analysis of three kinds of organic coating corrosion process, and the resin chain showed fracture fracture and C-O bond cleavage of the N-H bond. Therefore, it can be inferred that the effective components in the coating was damaged in the photochemical effect, accelerated chloride the corrosive media in the coating and the coating into the bubble, the failure of cracking and spalling corrosion phenomena. While in the coating film material corrosion resistance of polyurethane by modified and added coating of titanium dioxide in the coating system will be greatly improved. No coating system for surface treatment only supersonic flame spraying after four cycles to accelerate the experiment of serious corrosion, through XPS analysis, the coating surface coating system before the experiment without Fe elements exist after corrosion of iron element and the FeO, Fe3O4, F E2O3, FeOOH, Fe2 (SO4) has 3 forms: five kinds of oxide corrosion is not serious in parts of two valent iron than serious corrosion site, and Fe2 (SO4) 3 in the content of serious corrosion of parts, iron transformation process may be from stable Fe elemental and two valent iron oxide, in between after the ferric oxide, and finally the formation of ferric sulfate layer failure also showed the content of C/O is smaller than the corrosion will occur after HVOF spraying, and its main material to form the oxide WC may leave the protection coating on the base metal with the base metal is gradually lost, continue to suffer the corrosion of corrosive medium and destruction.

【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

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