Journal of South China University of Technology(Natural Science Edition) ›› 2012, Vol. 40 ›› Issue (1): 101-106,124.

• Materials Science & Technology • Previous Articles     Next Articles

Formation Mechanism and Properties of Colored Ti /Zr-Based Conversion Coating on Aluminum Alloy

Yi Ai-hua  Li Wen-fang  Du Jun  Mu Song-lin  Liu Ning-hua   

  1. School of Materials Science and Engineering,South China University of Technology,Guangzhou 510640,Guangdong,China
  • Received:2011-07-01 Revised:2011-09-05 Online:2012-01-25 Published:2011-12-01
  • Contact: 李文芳(1964-) ，男，教授，博士生导师，主要从事材料表面工程研究． E-mail: mewfl@sct.edu.cn E-mail:yiaihua92751@163.com
  • About author:易爱华(1980-) ，男，博士生，主要从事材料表面工程研究．
  • Supported by:

    粤港关键领域重点突破专项基金资助项目( 2008Z012) ; 广东省重大科技专项基金资助项目( 2009A08025002)

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Abstract:

In order to overcome the colorlessness of Ti /Zr conversion coatings applied in industry,a colored Ti /Zr conversion coating was prepared on the surface of aluminum alloy by adding tannic acid and film-forming accelerator in the treatment solution containing titanium and zirconium ions. Then,the growth process,morphology microstructure and corrosion resistance of the coating were characterized and analyzed by means of EDS,SEM,FT-IR,XRD,XPS and by using an electrochemical workstation. The results show that golden conversion coatings with strong corrosion resistance can be successfully prepared on the surface of aluminum alloy,that the coating mainly contains Na3AlF6,followed with the metal complexes of tannic acid hydrolysate and a small amount of Al2O3·3H2O and TiO2,that the formation of the golden coating undergoes a process consisting of nucleation,crystal growth and metal complex formation,and that the corrosion resistance of the coating greatly improves because there occurs a sharp decrease in corrosion current density from 5. 894 μA/cm2 to 0. 283 μA/cm2.

Key words: conversion coating, aluminum alloy, tannic acid, film formation mechanism, corrosion resistance