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Chem. J. Chinese Universities ›› 2006, Vol. 27 ›› Issue (5): 817.doi:

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Preparation, Structure and Properties of Molybdate Modified Zinc Phosphate Coating on Magnesium Alloy AZ91D

LI Guang-Yu, LIAN Jian-She*, NIU Li-Yuan, JIANG Zhong-Hao, JIANG Qing   

  1. Key Laboratory of Automobile Materials, Ministry of Education, College of
    Materials Science and Engineering, Jilin University, Changchun 130025, China)
  • Received:1900-01-01 Revised:1900-01-01 Online:2006-05-10 Published:2006-05-10
  • Contact: LIAN Jian-She

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Abstract:

Uniform and dense molybdate modified zinc phosphate coatings were formed on the magnesium alloy AZ91D surfaces by using a phosphating bath containing molybdtate and corrosion inhibitor. Phase components of coatings were analyzed by XRD. Morphology and compositions of coatings were analyzed by SEM and EDS. The results indicate that the phosphate coatings consist mainly of Zn3(PO4)2·4H2Oand Zn. When molybdate was added in the bath, phosphate coatings became denser and crackfree. The phosphate coatings obtained from the bath containing 1.5 g/L sodium molybdate exhibit denser microstructure and higher concentration of metallic zinc. A corrosion test estimating the corrosion resistance of conversion coating on magnesium alloy was proposed. Phosphating reaction mechanism on the magnesium alloy AZ91D surfaces was also investigated.

Key words: Magnesium alloy; Zinc phosphating; Corrosion resistivity; Sodium molybdate

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