Acta Metallurgica Sinica (English Letters) ›› 2009, Vol. 22 ›› Issue (1): 65-70.DOI: 10.1016/S1006-7191(08)60072-1

• Research paper • Previous Articles     Next Articles

Chemical conversion coating on AZ31B magnesium alloy and its corrosion tendency

Hualan JIN1, Xiangjie YANG2, Ming WANG2   

  1. 1.School of Materials Science and Engineering, Nanchang University, Nanchang 330031, China
    2.School of Mechanical and Electronic Engineering, Nanchang University, Nanchang 330031, China
  • Received:2008-04-10 Online:2009-02-25 Published:2009-10-10
  • Contact: Hualan JIN

Abstract:

The morphology change of the magnesium matrix after pre-treatment and the morphology as well as the phase composition of chemical conversion coating formed by phosphate were studied using scanning electron microscope and X-ray diffraction. The corrosion resistance of the coating was studied by salt spray and damp test, and the corrosion tendency during salt immersion test was analyzed. The results show that the phase composition before and after pre-treatment is almost changeless, and the deep microflaw appears between α and β phases during acidic pickling. The phosphate conversion coating is mainly composed of Mg, MgO, and some amorphous phase, and it can provide a good protection for the AZ31B alloy. Results from corrosive morphology indicate that the growth and the corrosion resistance of the phosphate conversion coating are related to the forming process of the AZ31B matrix.

Key words: Magnesium alloy, Phosphate, Chemical conversion coating, Corrosion resistance