Fe-N化合物与复合处理层抗腐蚀机理及组织性能研究

发布时间：2018-05-09 13:46

本文选题：Q235 + 气体多元共渗　；参考：《西南交通大学》2017年硕士论文

【摘要】：作为目前最重要的结构材料,金属的腐蚀不仅给国民经济带来了巨大的经济损失、惨重的环境污染和人员的伤亡,且造成资源浪费,加大了自然资源的损耗。防止金属的腐蚀和提高金属的耐蚀性是目前最引人注意的问题之一。西南交通大学自主研发的多元共渗技术能保证材料的高耐蚀性。目前从微观上(电子层面)对于该技术防腐蚀机理的认识还不够。为了进一步提高材料的耐蚀性,对多元共渗样品进行化学镀处理。结果表明复合处理(多元共渗+化学镀)后材料的耐蚀性进一步大幅度提高。本文主要采用多元共渗、多元共渗+化学镀复合处理工艺对Q235钢进行表面处理。对样品进行腐蚀性能测试,并运用经验价电子理论(EET)和"双电层"模型来探讨了其腐蚀机理。结果表明:经过多元共渗处理后样品的自腐蚀电位提高,自腐蚀电流下降,材料的耐腐蚀性较原材大幅度地提高。阻抗谱分析与扫描电子显微镜(SEM)结果显示多元共渗渗层的腐蚀形式为点蚀,且点蚀的发生与化合物层的柱状晶组织、缺陷如显微孔洞、高浓度的活性阴离子Cl-有关。复合处理工艺处理的样品的击破电位达到了 1.346V,盐雾腐蚀300h不生锈。复合处理后,其耐蚀性远远高于单一多元共渗和化学镀处理。经验价电子理论结果表明Fe4N、Fe3N、Fe2N、Ni、α-Fe 的最强健上价电子数叫分别为 0.9552、1.83、2.4239、0.5251、0.3835;最强健的键能 Eα分别为 156kJ/mol、361.4kJ/mol、437.8kJ/mol、201kJ/mol、107.4kJ/mol。Fe-N化合物的nα、Eα都远远大于α-Fe的nα、Eα,表明价电子结构与腐蚀之间有着密切的关联性。Fe-N化合物层和Ni层的费米能计算结果表明Fe-N化合物层的费米能高于Ni层的费米能。根据电化学腐蚀原理对于腐蚀的定义M-ne-→Mn+,可以理解腐蚀的本质就是原子间电子的"转移"。而价电子是原子间连接的基础。所以可以用原子间的价电子结合强度来判断材料的耐蚀性优劣。即从热力学上来说,nα、Eα越大,材料耐蚀性越好。费米能计算结果表明Fe-N化合物层的费米能高于Ni侧的费米能。Fe-N化合物层的电子向Ni侧"转移",形成了 Fe-N化合物层过剩正电荷,Ni侧过剩负电荷,从而形成了"双电层"。正是"双电层"的存在,使得复合处理工艺处理的样品耐蚀性进一步大幅度地提高。
[Abstract]:As the most important structural material at present, metal corrosion has not only brought huge economic losses, heavy environmental pollution and casualties to the national economy, but also caused waste of resources and increased the loss of natural resources. One of the most noticeable problems is to prevent metal corrosion and to improve metal corrosion resistance. The multi-percolation technology developed by Southwest Jiaotong University can guarantee the high corrosion resistance of the materials. At present, the microcosmic (electronic level) understanding of the anti-corrosion mechanism of the technology is not enough. In order to further improve the corrosion resistance of the materials, electroless plating was carried out on the multicomponent co-permeated samples. The results show that the corrosion resistance of composite treatment (multicomponent electroless plating) is further improved. In this paper, the surface of Q235 steel was treated by multi-element co-infiltration and multi-element electroless plating. The corrosion mechanism of the samples was investigated by using empirical valence electron theory (EET) and "double layer" model. The results showed that the corrosion potential of the samples was increased, the corrosion current was decreased, and the corrosion resistance of the materials was greatly improved than that of the raw materials. The results of impedance spectroscopy and scanning electron microscopy (SEM) show that the corrosion of the multielement layer is pitting, and the pitting is related to the columnar structure of the compound layer, defects such as micropores and high concentration of active anions Cl-. The breakdown potential of the sample treated by the complex treatment process was 1.346V, and the salt spray corrosion was not rusty for 300h. The corrosion resistance of composite treatment is much higher than that of single multi-element co-permeation and electroless plating. The results of empirical valence electron theory show that the strongest valence electron number of 伪 -Fe is 0.9552U 1.832.4239U 0.5251N 0.3835, and the strongest bond energy E 伪 is 156kJ / mol / 361.4kJ / mol 437.8kJ / mol = 201kJ / mol = 107.4kJ / r = 107.4kJ / mol = 107.4kJ / r = 107.4kJ / mol = 107.4kJ / mol = 107.4kJ / r = 107.4kJ / The Fermi energy of Fe-N compound layer and Ni layer shows that the Fermi energy of Fe-N compound layer is higher than that of Ni layer. According to the definition of corrosion by electrochemical corrosion principle, M-ne- mn can be understood that the essence of corrosion is the "transfer" of electrons between atoms. Valence electrons are the basis for interatomic connections. Therefore, the corrosion resistance of the materials can be judged by the valence electron bonding strength between atoms. That is to say, the larger the thermodynamics, the better the corrosion resistance of the material. The Fermi energy calculation results show that the Fermi energy of the Fe-N compound layer is higher than that of the Ni side Fermi energy. Fe-N compound layer "transfers" electrons to the Ni side, forming the excess positive charge of the Fe-N compound layer and the excess negative charge on the Ni side, thus forming the "double electric layer". Because of the existence of double layer, the corrosion resistance of the samples treated by the composite treatment process is further improved.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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