摘要
化学转化膜技术是金属物件表面处理过程中应用广泛的一项技术。转化膜对金属基底有较好的防护作用,但在成膜过程中,因微阴极区域存在剧烈的析氢反应,以及在成膜结束干燥过程中失水导致转化膜收缩,使得所形成的转化膜结构疏松,膜层裂纹增多。裂纹破坏了转化膜层的紧密度,为腐蚀性介质提供了有效的通道,严重削弱了膜层的保护作用。本文首先介绍了各类环保、无铬的化学转化膜及其制备技术,并分析了转化膜存在微裂纹的原因。针对转化膜表面有微裂纹和耐蚀性不佳的缺点,技术人员通过多种技术来改进所得膜层的连续性和耐蚀性。目前,对于降低转化膜开裂程度方面的研究主要集中在向转化液中添加不同添加剂、采用后处理手段密封孔道等。本文重点阐述了转化膜膜层致密化及提升其耐蚀性能的工艺优化进展,着重分析了转化膜制备过程中添加不同添加剂和进行后处理的工艺技术。可使转化膜致密的添加剂有金属离子、纳米粒子、成膜促进剂和表面活性剂。而在转化膜制备过程中,向转化液中添加不同的添加剂,其对所形成的转化膜的致密机理不同,致密程度也有一定的差异,但工艺相对简单。当对制备的转化膜进行后处理时,主要用磷酸二氢盐、溶胶-凝胶、不同于基膜的成膜材料和热处理技术等,各种后处理技术也能提升转化膜层对金属基底的保护效率。本文总结归纳了提到的各种工艺的优缺点、致密化原理及所制备的膜层对基底的防腐蚀保护效果。在文献归纳的基础上,还对转化膜技术在金属表面转化处理的发展方向进行了展望。
Chemical conversion coating technology is widely applied in the metal surface treatment which has a good protective effect for the metal anti-corrosion.However,during the coating formation process,the coating shrinks due to the severe hydrogen evolution reaction in the micro-cathode area and the loss of water during the drying process at the end of the coating formation,resulting in loose structure of the formed conversion coating and increased cracking of the coating layer.Crack damages the tightness of the coating,provides an efficient channel for corrosive medium and seriously weakens the protective effect of coating.This paper first introduces various environmentally friendly,chromium-free chemical conversion coatings and their preparation techniques,and analyzes the causes of micro-cracks in the conversion coating.In view of the defects of micro-cracks and poor corrosion resistance of various conversion coatings,researchers improved the continuity and corrosion resistance of the obtained conversion coating through various technologies.At present,the research on reducing the degree of cracking of the conversion coating mainly focuses on the following aspects,adding diffe-rent additives to the conversion solution,and adopting post-treatment means to seal the pores and the like.This paper focuses on the process optimization progress of the densification and corrosion resistance improvement of the conversion coating and focuses on the analysis of the process technology of adding different additives and post-treatment in the preparation process of the conversion coating.Additives that can be used for densification include metal ions,nano-particles,film-forming accelerators,and surfactants.In the preparation process of the conversion coating,different additives are added to the conversion solution,different additives have different densification mechanisms for the formed conversion coating and the degree of compactness also has a certain difference.Only different additives are added to the conversion solution and the process is relatively simple.However,when post-treatment of the prepared conversion coating is carried out,it is mainly using dihydric phosphate,sol-gel,film-forming materials different from the substrate coating and heat treatment technology.Various post-treatment technologies can also improve the protection efficiency of the coating.The advantages and disadvantages of the various processes mentioned above,the mechnism of densification and the anti-corrosion protection effect of the prepared coating on the substrate are summarized in detail.On the basis of literature summarization,the development direction of conversion coating technology on metal surface treatment is also prospected.
作者
卢勇
冯辉霞
LU Yong;FENG Huixia(School of Petrochemical Engineering,Lanzhou University of Technology,Lanzhou 730050,China;Research Institute of Lanzhou Petrochemical Corporation of Petrochina,Lanzhou 730060,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2020年第13期13160-13166,共7页
Materials Reports
基金
国家科技部“科技人员服务企业行动项目”(2009GJG10041)
甘肃省高校基本科研业务费(1105ZTC136)。
关键词
转化膜
致密性
耐蚀性
工艺优化
conversion coating
densification
corrosion resistance
process optimization
