【作者】 邹忠利；

【导师】 李宁；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2011， 博士

【摘要】 为了满足电镀锌板高质量高性能的要求,近年来出现了耐指纹处理这种新型表面处理技术。由于耐指纹板具有较高的产品附加值,已经广泛地应用于汽车、航空、电气和家用等领域。目前电镀锌板耐指纹处理的传统方法是使用铬酸盐复合有机树脂涂料液进行处理,由于涂覆过程中使用的六价铬具有致癌性,对人体和环境都有严重的危害。迄今为止国内外尚未出现一种无铬处理可以在耐蚀性方面完全替代铬酸盐处理。因此需要寻找一种环境友好且具有良好耐蚀性的耐指纹处理方法。耐指纹处理液是由无机组分和有机组分两部分组成,本文的研究思路是分步进行研究。首先进行无机氧化剂的研究,采用钒酸盐作为成膜主盐在电镀锌板表面制备新型的化学转化膜——钒酸盐转化膜。单因素试验研究钒酸盐处理液的pH值、成膜温度、成膜时间及钒酸盐浓度等工艺条件的影响。通过正交实验优化确定制备工艺,结果如下:钒酸盐浓度为30g/L,pH值为6,成膜温度为20℃,成膜时间10min。利用扫描电子显微镜(SEM)、能谱分析仪(EDS)、X射线光电子能谱(XPS)及盐雾试验(NSS)等技术手段研究转化膜的微观组织形貌、成分、结构及耐蚀性等性能。XPS结果显示转化膜主要是由五价钒的氧化物或氢氧化物组成,并含有少量的四价钒及二价锌的氧化或氢氧化合物;结合电化学测试等结果提出转化膜的形成过程可分为锌溶解、稳定成膜、转化膜溶膜三个阶段。由此提出可能的成膜机理,认为转化膜的形成可能是基体的溶解和转化膜的沉积两者共同作用的结果;借助EIS等技术研究了锌基体表面钒酸盐转化膜在3.5wt% NaCl溶液浸泡过程中的腐蚀行为,深入分析了转化膜的失效机制。采用钒酸盐复合有机树脂涂层构成耐指纹处理体系以优化膜层防护性能,通过试验筛选采用水性丙烯酸作为成膜剂,钒酸盐和L-抗坏血酸作为混合氧化剂,纳米SiO2作为阻隔剂,硅烷偶联剂KH560作为界面改性剂,磷酸作为酸度调节剂。通过形貌观察、耐蚀性及组成测试考察了复合有机树脂涂层的性能。结果显示自制的钒酸盐复合有机树脂涂层具有较平整的表观形貌,优于同类商品涂层的耐蚀性能。硅烷偶联剂的分子桥作用使纳米SiO2、钒酸盐等无机物与水性有机丙烯酸树脂桥连在锌基体表面实现复合成膜。通过NSS及量化计算等方法对这一过程进行了验证。最后对锌基体表面复合有机涂层的形貌、结构、耐蚀性及其成膜过程等进行了系统地研究。硅烷偶联剂具有独特的结构和性能,在金属表面处理方面有着广泛地应用。试验研究了KH171、KH570及KH560三种硅烷偶联剂的水解工艺,采用电导率法表征硅烷的水解过程,电化学测试结果表明硅烷水解工艺经过两次水解过程可以使硅烷水解液更加稳定。结果还显示二次水解工艺能够使硅烷膜具有良好耐蚀性,三种硅烷水解液中以KH560得到膜层的耐蚀效果最好。采用两步法工艺得到钒酸盐复合硅烷涂层,即先在锌基体表面涂覆硅烷膜,然后再通过钒酸盐处理液进行处理的方式来制备复合膜。通过SEM观察复合膜前后的表观形貌;XPS和红外光谱测试了复合硅烷膜的表面组成和结构;采用中性盐雾试验和电化学方法测量了复合涂层的耐蚀性能。试验结果表明:复合硅烷膜的表面形貌相对于单纯硅烷膜,其表面的微裂纹明显减少;XPS和红外光谱结果显示硅烷膜可以与锌基体表面紧密键合;耐蚀性测试结果显示复合硅烷膜具有极佳的耐蚀性,这是由于其良好的微观结构。对复合硅烷膜在3.5wt% NaCl溶液中浸泡不同时间的研究结果表明:复合膜的失效机制分为三个阶段,即浸泡初期、浸泡中期和浸泡后期。分别采用不同的等效电路图对各阶段相应的膜层结构变化对进行了合理解释。更多还原

【Abstract】 To meet the requirements of high quality and performance of electrogalvanized steel sheet, a new surface treatment which is called anti-fingerprint treatment has been developed in recent years. The anti-fingerprint plate has been widely used in automotive, aerospace, electrical and domestic areas due to its high added value. However, the anti-fingerprint treatment baths are usually prepared with hexavalent chromium, which are carcinogenic and harmful to human health and environment. Nowadays , there is no non-chromium anti-fingerprint treatment which can substitute chromium treatment. Therefore, new alternative and more environmentally friendly anti-fingerprint treatments need to be developed.Anti-fingerprint treatment baths are composed of inorganic and organic parts. The research idea was to study the components of friendly anti-fingerprint treatment for electrogalvanized steel (EG) plates separately. Firstly, inorganic oxidants were studied. The vanadate conversion coating as chromate replacement was prepared on EG plates previously treated in a solution mainly composed of vanadate in this paper. Influences of pH value, film forming temperature, film forming time and vanadate concentration on the conversion coating were studied by the single factor experiments respectively. Next, the preparation process was determined through the orthogonal experiments. The optimum processing parameters of vanadate conversion coating were confirmed as follows: vanadate solution concentration is 30g/L, pH value of solution is 6, treating temperature is 20℃, and treating time is 10 min. The morphology, composition, structure and corrosion resistance of the coating were investigated by using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), X-ray photoelectron spectroscopy (XPS) and neutral salt spray test (NSS) respectively. The film mainly consists of vanadium and oxygen, which mainly exist as the oxides or its hydrates of V5+ as well as a small amount of oxide or its hydroxide of V4+ and Zn2+ according to the XPS results. The formation process and mechanism of the conversion coating were proposed by using the results combining the electrochemical measurements. The formation process can be divided into three steps: dissolution of zinc, stable film formation and dissolution of film. The possible formation mechanism was proposed that the formation of the vanadate conversion coating is cooperated with the dissolution of zinc substrate and the deposition of conversion coating. The corrosion behavior and failure mechanism of vanadate conversion film were in depth investigated by using EIS with the film immersed in 3.5wt% NaCl solution for different times.Performances of the coating were further optimized by using vanadate/organic resin composite system (namely anti-fingerprint treatment system). Water-based acrylic resin was selected as the film-forming agent, mixture of L-ascorbic acid and vanadate as a mixed oxidant, nano-SiO2 as a barrier agent, silane coupling agent KH560 as an interface modifier and phosphoric acid as acidity regulator. The surface morphology, composition and corrosion resistance of the complex coating were studied respectively. The results showed that there was a more flat morphology for the vanadate/organic resin composite coating and corrosion resistance of the complex coating was much better than that of the similar products. Inorganic additives such as nano-SiO2 and vanadate were connected to the water-based acrylic resin by the molecular bridge of silane coupling agent; the methods of NSS and quantum chemical calculation were used to describe this process. Finally, the morphology, structure, corrosion resistance and its formation process of the composite coating were investigated by SEM, XPS, NSS and EIS.Silane coupling agent has been widely used in the the field of surface treatment of metals, based on its unique structure. Firstly, researches on the hydrolysis of three silane coupling agents (KH171, KH570 and KH560) were carried out in this paper. The hydrolysis process of silane was characterized using the method of conductivity, which indicated that the process was comprised of two hydrolysis steps. The reasonable concentration of silane solution was determined by the electrochemical tests. The results of hydrolysis showed that the silane solution was more stable after the second hydrolysis, and corrosion resistance of the coating prepared from KH560 solution was the best among three solutions. Secondly, a two-step method was used to prepare the vanadate/silane composite coating. The silane film was firstly made on the surface of zinc substrate, and then the sample was immersed in vanadate treatment solution. The morphology, composition and structure of the composite coating were investigated by SEM, XPS and infrared spectra (IR), and corrosion resistance of the coating was analyzed by NSS and electrochemical tests. The surface micro-cracks of composite coating were significantly reduced compared with that of simple silane treated film. XPS and IR results showed there were some chemical bonds between the silane film and the zinc substrate. Corrosion test results showed that the better microstructure of the composite silane film had more excellent corrosion resistance. The corrosion resistance results of films with different immersion time in 3.5wt% NaCl solution showed that the failure process can be divided into three stages: chloridion absorption, conversion coating dissolution and penetration into the coating. Different equivalent electrical circuits were used to explain the structure of the composite film.更多还原