Journal of Inorganic Materials ›› 2015, Vol. 30 ›› Issue (6): 627-632.doi: 10.15541/jim20140582

• Orginal Article • Previous Articles     Next Articles

Effect of Sealing Treatments on the Corrosion Behavior of Micro-arc Oxidation Coating on Aluminum Alloy in Acid NaCl Solution

Zuo-Yan YE1(), Dao-Xin LIU1(), Chong-Yang LI1, Xiao-Hua ZHANG1, Xiao-Ming ZANG2, Ming-Xia LEI2   

  1. 1. Corrosion and Protection Research Laboratory, Northwestern Polytechnical University, Xi'an 710072, China
    2. AVIC the First Aircraft Institute, Xi'an 710089, China
  • Received:2014-11-14 Revised:2014-12-25 Online:2015-06-04 Published:2015-05-22
  • About author:YE Zuo-Yan. E-mail: yebonpu@126.com
  • Supported by:
    National Natural Science Foundation of China (51171154);National Defense key Disciplines Laboratory of light Alloy Procossing Science and Technology, Nachang Hangkong University (gf201401001)

Abstract:

Ceramic coatings were fabricated on 7A85 aluminum alloy by unipolar positive pulsed micro-arc oxidation (MAO) treatment for enhancing corrosion resistance. A bi-layer coating was formed with large pores between the layers. The outer layer contained several micro pores and cracks. Therefore, cerium nitrate, potash bichromate and SiO2 sol were adopted to seal the MAO coatings. Scanning electron microscope, X-ray diffraction and electrochemistry instrument were used to investigate the effect of sealing treatments on the surface morphology, coating structure and corrosion resistance of MAO coatings. Results show that the MAO coating can not protect aluminum alloy from acid NaCl solution for the existing of defects. The defects can be sealed by precipitations produced by cerium nitrate and potash bichromate sealing treatment, and corrosion resistance of the MAO coating is improved. However, the sealed coatings also fail in the acid NaCl solution for dissolution of the precipitation. After sealing with SiO2 sol, the MAO coating is covered with a SiO2 gel layer has become a compact barrier layer to protect aluminum substrate from corrosion in acid NaCl solution.

Key words: aluminum alloy, micro-arc oxidation, seal treatment, electrochemistry, corrosion resistance, SiO2 sol

CLC Number: 

  • TQ174