不锈钢表面纳米复合防护多层涂层的研究

发布时间：2018-04-29 10:11

本文选题：聚苯胺 + 聚丙烯酸　；参考：《南京大学》2015年博士论文

【摘要】：不锈钢具有高机械强度和良好的耐腐蚀性,因而被广泛用于工业生产及大型工程结构中的骨架材料。但不锈钢的热力学性能不稳定,暴露在含氯环境中容易被腐蚀。当它与含氯环境接触时,腐蚀反应会在其表面发生,从而破坏或降低钢结构的完整性。众所周知,金属腐蚀会导致严重的经济损失,每年全球为此消耗万亿美元。因此,发展新型、智能并且环境友好的防腐涂层材料是延长不锈钢使用寿命,提高其在国际市场上竞争力的重要途径。为了最大限度减少经济损失,近年来人们在有机抑制剂、智能、多功能涂层开发方面进行了深入研究,许多针对不同恶劣环境中不锈钢防腐的有效方法被提出。主要包括：(1)使用有机杂原子作为抑制剂。有机杂原子被认为是保护不锈钢免受腐蚀引起性能恶化的重要材料,特别是在酸性介质中。作为保护膜,有机杂原子吸附在金属表面上,在酸性介质中形成阻碍腐蚀性物质与金属表面接触的物理屏障。(2)使用能够持久抗腐蚀保护的有机涂层。其中,以导电聚合物为基础的“智能”复合涂层,即使金属表面存在缺陷的区域暴露于腐蚀环境中也能有效防止腐蚀。聚苯胺被认为是导电聚合物中最好的防腐蚀材料,因为它可以存在于不同的状态下(氧化/还原状态),并且在适当条件下,这些状态之间很容易相互转换,聚苯胺经历氧化还原过程后在金属表面诱导形成钝化氧化层。然而,聚苯胺在水溶液中非常差的溶解性限制了其在涂层材料和腐蚀抑制剂中的应用。(3)使用功能性有机涂层。“智能”涂料的概念已被应用于功能性涂料,例如,功能性涂层具有针对内在或外在事件能产生某种刺激响应的自修复能力。这一自修复能力可通过释放包裹在纳米反应器中的修复剂来实现。为了避免添加的修复剂在反应体系中可控释放困难的问题,自身有自修复能力的材料表现出很好的优势。然而,自修复机理目前尚不清楚,利用聚电解质自组装膜对一些严重损伤进行自修复仍具有一定的挑战性。设计组装多层结构可以将智能和功能性有机涂层相结合,通过一些常用的方法就能够实现,如喷涂、浸渍和旋涂。其中,浸渍和旋涂可以精确控制涂层的组成和厚度,通过浸渍涂布和使用层叠技术制备聚电解质自组装的纳米网络;旋涂也是一种容易和可靠的方法,但由于涂层的形态受溶剂类型、浓度和湿度的显著影响,造成涂层耐腐蚀性的可控性降低。基于以上讨论,利用可加工的聚苯胺复合物为抑制剂,以及组装成多层结构是一种提高涂层在侵蚀性环境下保护能力的理想途径。此外,涂层的制备参数,例如溶液浓度(c)和盘旋转速度(ω),电解液的扩散行为和浸渍溶液的pH值等,都会在多层组装过程中影响涂层的厚度和耐腐蚀性。因此,通过在调整工艺参数,开发智能、具有自修复和氧化还原催化性能的防腐涂料,是不锈钢防腐领域中的研究重点。本工作的目的是采用以上所述的这三种策略,得到智能的防腐效果,实现在不同环境中保护不锈钢。本论文中,我们采用一步原位聚合法制备了具有优异的加工性和导电性的水溶性聚苯胺-聚丙烯酸(PANI-PAA)复合材料。并研究了这些复合材料在强酸性介质中对316不锈钢的防腐保护性能。然后,我们采用旋涂法装制备了聚苯胺-PAA/PEI多层结构的复合材料,研究了层数对聚苯胺-PAA/PEI防腐蚀性能的影响,并优化了防腐蚀保护性能。在旋涂组装期间,优化了诸如c和ω等因素,获得了厚度可控的多层结构。基于对多层结构内扩散行为的系统研究,探讨了耐腐蚀性增强的机理。此外,我们还研究了PDDA/PAA多层涂层的应激自修复行为。研究工作主要包括如下几个方面：(1)水溶性PANI-PAA复合物的制备。通过在绝缘基质(如PAA)中进行苯胺单体的聚合,可显著提高PANI的水溶性。PAA作为基质不仅提高聚苯胺在水中的溶解度,而且还防止聚苯胺团聚体的形成。抑制剂在316SS表面的吸附过程满足Langmuir吸附等温线,在优化PAA浓度为200 ppm条件下制得的PANI-PAA的抑制效率最佳。防腐性的提高是由于PANI-PAA吸附形成的绝缘界面层抑制了界面处的腐蚀反应。(2)采用交替沉积法制备多层结构的聚苯胺-聚丙烯酸／聚乙烯亚胺(PANI-PAA/PEI)复合涂层。旋涂过程中加热有助于残留水分的去除,这使得多层膜的厚度与层数量(n)呈线性增加的关系。PANI-PAA复合物与PEI的结合以及多层结构实现了对316不锈钢耐腐蚀性的协同增强。有趣的是,PANI-PAA/PEI涂层的防腐蚀保护性能在n=20时最佳。我们认为：这应归因于界面氧化物层的形成,以及多层结构延长了腐蚀性离子的扩散路径。(3)制备了厚度在0.47至2.94微米范围内可调的PANI-PAA/PEI涂层。由于具有电活性与氧化还原催化能力,使得涂层的防腐蚀保护效率大幅提高。该涂层后在3.5%NaCl溶液中浸泡120小时仍稳定,电解质在涂层内的扩散行为是时间的函数。基于系统研究,我们提出了涂层对电解液在多层结构内扩散行为产生影响的机制。(4)制备了具有显著刺激响应性自修复和抗腐蚀能力的聚二甲基二氯(PDDA)／聚丙烯酸(PAA)多层涂层材料。采用层叠(LBL)技术,我们能够对层数(n)和涂层厚度进行精确控制。研究了该涂层针对430不锈钢的防腐性能,以及涂层自修复性能对层数的依赖性。结果表明,自修复归因于刺激响应肿胀和聚电解质多层膜在划痕附近的静电修复。抗腐蚀能力的提高主要是由于多层结构的自修复功能及其延长并阻碍了腐蚀性物质的扩散通路。
[Abstract]:Stainless steel has high mechanical strength and good corrosion resistance, so it is widely used in industrial production and skeleton materials in large engineering structures. However, the thermodynamic properties of stainless steel are unstable and exposed to corrosion in the chlorine containing environment. When it contact with the chlorine containing environment, the corrosion should occur on its surface, thereby destroying or reducing steel. It is well known that metal corrosion will lead to serious economic losses and consume trillions of dollars a year worldwide. Therefore, the development of new, intelligent and environmentally friendly anticorrosive coating materials is an important way to prolong the service life of stainless steel and to improve its competitiveness in the international market. To minimize economic losses, In recent years, people have studied the development of organic inhibitors, intelligent and multifunctional coatings. Many effective methods for stainless steel corrosion in different harsh environments have been proposed. (1) the use of organic hetero atoms as inhibitors is considered to be important to protect stainless steel from corrosion. Material, especially in acid medium. As protective film, organic heteroatoms adsorb on metal surfaces, form a physical barrier that impede contact between corrosive substances and metal surfaces in acid medium. (2) use an organic coating that can endure corrosion protection. Areas with defective surfaces can also be exposed to corrosion in a corrosive environment. Polyaniline is considered to be the best anticorrosion material in conductive polymers, because it can exist in different states (oxidation / reduction state), and under appropriate conditions, these states are easily converted to each other, and polyaniline is redox through oxidation and reduction. Passivating oxidation layer is induced on the surface of metal. However, the very poor solubility of Polyaniline in aqueous solution restricts its application in coating materials and corrosion inhibitors. (3) the use of functional organic coatings. The concept of "intelligent" coatings has been applied to functional coatings, for example, functional coatings are intrinsic or external. The self repair capability of an event can produce some kind of stimulus response. This self repair ability can be achieved by releasing a reparative agent wrapped in a nano reactor. In order to avoid the problem that the added restorant can release the difficult problem in the reaction system, the self repairing material has a good advantage. However, the self repair mechanism is present. It is not clear that the use of polyelectrolyte self assembly membranes is still challenging to self repair some serious damage. The design and assembly of multilayer structures can be combined with intelligent and functional organic coatings, such as spraying, impregnation and spin coating, in which impregnation and spin coating can be used to control the coating accurately. The composition and thickness of Nanonetworks with self assembly of polyelectrolyte are prepared by impregnation coating and stacking technology; spin coating is also an easy and reliable method, but because the morphology of the coating is affected by the type of solvent, concentration and humidity, the controllability of the corrosion resistance of the coating is reduced. Based on the above discussion, the machinable polyphenylene is used. In addition, the preparation parameters of the coating, such as solution concentration (c) and disk rotation speed (omega), the diffusion behavior of the electrolyte and the pH value of the impregnated solution, will affect the thickness of the coating during the multi-layer assembly process. Therefore, by adjusting the process parameters, developing the intelligent anticorrosion coatings with self repairing and redox catalytic properties, it is the focus of research in the field of stainless steel anticorrosion. The purpose of this work is to use the above three strategies to obtain the antiseptic effect of intelligent corrosion protection and to realize the protection of stainless steel in different environments. In this paper, we have prepared a water-soluble polyaniline polyacrylic acid (PANI-PAA) composite with excellent machinability and conductivity by one step in situ polymerization, and studied the anticorrosion and protection properties of these composites on 316 stainless steel in strong acidic medium. Then, we have prepared the polyaniline -PAA/PEI multilayer structure by using the spin coating method. The influence of the number of layers on the corrosion resistance of polyaniline -PAA/PEI was studied and the corrosion protection performance was optimized. During the spin coating assembly, the factors such as C and Omega were optimized, and the thickness controlled multilayer structure was obtained. Based on the systematic study of the diffusion behavior in the multilayer structure, the mechanism of corrosion resistance enhancement was discussed. In addition, I The stress self repair behavior of PDDA/PAA multilayer coatings is also studied. The research work mainly includes the following aspects: (1) preparation of water-soluble PANI-PAA complexes. By polymerization of aniline monomers in the insulating matrix (such as PAA), the water-soluble.PAA of PANI can be significantly increased as the matrix not only to increase the solubility of Polyaniline in water, but also to improve the solubility of Polyaniline in water. The formation of polyaniline aggregates is also prevented. The adsorption process of the inhibitor on the surface of the 316SS satisfies the Langmuir adsorption isotherm, and the inhibition efficiency of the PANI-PAA obtained by optimizing the PAA concentration of 200 ppm is the best. The anticorrosion is due to the corrosion reaction under the interface layer of the insulating interface formed by PANI-PAA adsorption. (2) the use of alternation. Polyaniline polyacrylic acid / polyethyleneimine (PANI-PAA/PEI) composite coating has been prepared by deposition. During the process of spin coating, heating helps to remove the residual moisture. This makes the thickness of the multilayer film increasing linearly with the number of layers (n). The bonding of the.PANI-PAA complex with the PEI and the corrosion resistance of the 316 stainless steel to the multilayer structure It is interesting that the anticorrosion protection performance of the PANI-PAA/PEI coating is best at n=20. We think that this should be attributed to the formation of the oxide layer of the interface and the extension of the diffusion path of the corrosive ions by the multilayer structure. (3) the PANI-PAA/PEI coating with adjustable thickness in the range of 0.47 to 2.94 microns is prepared. The anti-corrosion protection efficiency of the coating is greatly improved by the catalytic activity and redox catalytic ability. After the coating is soaked in 3.5%NaCl solution for 120 hours, the diffusion behavior of the electrolyte in the coating is a function of the time. Based on the system study, we put forward the mechanism that the coating affects the diffusion behavior of the electrolyte in the multilayer structure. (4) a polymethyl two chloride (PDDA) / polyacrylic acid (PAA) multilayer coating material with significant response to self repair and corrosion resistance is prepared. Using LBL technology, we can accurately control the layer number (n) and coating thickness. The corrosion resistance of the coating to 430 stainless steel and the self repair performance of the coating to the layer are studied. The results show that the self repair is attributable to the swelling of the stimulus response and the electrostatic repair near the scratch of the polyelectrolyte multilayer film. The improvement of corrosion resistance is mainly due to the self repair function of the multilayer structure and its extension and hindering the diffusion pathway of the corrosive substances.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG174.4

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