铬酸盐转化膜性能的研究进展

Research Progress on Chromate Conversion Coating Properties

化学转化膜工艺是轻合金复杂结构件最经济、最有效的表面处理方法。六价铬转化膜是工业界应用最多也是最成功的转化膜,然而,转化膜中的Cr6+对操作人员的健康危害很大;三价铬转化膜因其毒性低且具有铬酸盐转化膜的高效耐蚀等特点,成为最具前景的替代工艺。近年来的研究发现,在三价铬转化膜中存在六价铬组分(<0.1%,原子分数),而且Cr6+组分的分布和含量与反应溶液、后处理方法和腐蚀环境密切相关。铬酸盐转化膜的化学性能主要取决于其铬酸盐价态及变化。鉴于此,探讨膜层中六价铬组分形成机理、浓度控制和产生条件成为当下亟待解决的问题。本文简要介绍了化学转化膜的种类、成分、结构和成膜条件,讨论了铬酸盐转化膜的自修复性能、形成过程和结构以及应用现状,重点讨论了三价铬转化膜中六价铬组分的表征、膜层中六价铬组分形成机理及Cr6+组分浓度和产生条件的控制,并总结和展望了铬酸盐转化膜未来的研究思路。

The chemical conversion coating is the most economical and effective surface treatment method for light alloy complex structural parts.Hexavalent chromium conversion coating is the most widely used and the most successful conversion coating process in the industry.However,the Cr6+ in the conversion coating is very harmful to the operator’s health. The trivalent chromium conversion coating is the most promising alternative due to its low toxicity and high corrosion resistance.Therecent studies have found that hexavalent chromium components( < 0.1 at%) exist in trivalent chromium conversion coatings,and the distribution and content of Cr6+ components are closely related to the reaction solution,post-treatment methods and corrosive environment. It can be seen that the chemical properties of chromate conversion coating are mainly determined by their chromate valence and changes. In view of this,it is urgent to investigate the formation mechanism,concentration control and production conditions of the hexavalent chromium component in the coating.This paper briefly introduces the types,compositions,structures and coating forming conditions of chemical conversion coatings,discusses the self-repairing properties,formation process and structure of chromate conversion coatings,and the application status. The characterization of the hexavalent chromium component in the trivalent chromium conversion coating,the formation mechanism of the hexavalent chromium component in the coating and the control of the concentration and production conditions of the Cr6+ component are emphatically discussed,and summarizes and looks forward to the current and future research of chromate conversion coatings.