Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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The Composition of the Rare Earth Based Conversion Coating Formed on AZ91D Magnesium Alloy

  • Chang, Menglei (School of Science, Foshan University) ;
  • Wu, Jianfeng (School of Science, Foshan University) ;
  • Chen, Dongchu (School of Science, Foshan University) ;
  • Ye, Shulin (School of Mechanical and Electrical Engineering, Foshan University)
  • Received : 2017.12.18
  • Accepted : 2018.01.29
  • Published : 2018.02.28
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Abstract

As structural materials, magnesium (Mg) alloys have been widely used in the fields of aviation, automobiles, optical instruments, and electronic products. There are few studies on the effect of coating conditions on the compositional variation during the formation process of the conversion coatings. Rare-earth based conversion coating on AZ91 magnesium alloy was prepared in ceric sulfate and hydrogen peroxide contained solution. The element composition and valence as well as their distribution in the coating were analyzed with energy dispersive X-ray spectroscopy (EDS), Electron probe micro-analyzer (EPMA), X-ray photoelectron spectroscopy (XPS). The effect of treating process on the element composition were also studied. It was found that the conversion coating surface consists of Mg, Al, O, Ce, and the weight content of Ce in the coating was affected by the treating solution concentration and immersion time; the Ce element was distributed in the coating non-uniformly and existed in the form of $Ce^{+3}$ and $Ce^{+4}$, while the O element existed in the form of $OH^-$, $O^{2-}$, $H_2O$. Based on microscopic analysis results, the electrochemical deposition mechanism on the micro-anode and micro-cathode in the process of the coating growth was suggested.

Keywords

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Fig. 1 The elements distribution for (a) Mg, (b) Al, (c) Ce and (d) O in the conversion coating obtained by EPMA.

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Fig. 2 The elements distribution in the cross-section of theconversion coating on Mg alloy detected by EPMA.

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Fig. 3 XPS spectra of the conversion coating, (a) full range surveyed spectra; (b) oxygen 1s spectra; (c) Ce Cerium 3d spectra.

Table 1 The elemental composition of conversion coatings treated under different process conditions (mass)%

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References

  1. R. Fu, Automob. Technol. Mater., 7, 71 (2004).
  2. B. Li and Z. Shen, J. Mater. Protect., 35, 1 (2002).
  3. J. Wang and Y. Ding, J. Mater. Protect., 39, 38 (2006).
  4. H. Umehara, M. Takaya, and S. Terauchi, Surf. Coat. Technol., 169-170, 666 (2003). https://doi.org/10.1016/S0257-8972(03)00052-5
  5. J. Qian, D. Li, and B. Guo, J. Mater. Protect., 35, 5 (2002).
  6. L. Li, J. Lei, S. Zhang, D. Li, and Y.-J. Tian, J. Mater. Eng., 10, 60 (2006).
  7. Y. Xu, X. Chen, Z.-S. Lu, and Y.-J. Li, J. Chin. Rare Ear. Soc., 23, 40 (2005).
  8. M. F. Montemor, A. M. Simoes, and M. J. Carmezim, Appl. Surf. Sci., 253, 6922 (2007). https://doi.org/10.1016/j.apsusc.2007.02.019
  9. M. Dabala, K. Brunell, E. Napolitani, and M. Magrini, Surf. Coat. Technol., 172, 227 (2003). https://doi.org/10.1016/S0257-8972(03)00336-0
  10. A. L. Rudd, C. B. Breslin, and F. Mansfeld, Corros. Sci., 42, 275 (2000). https://doi.org/10.1016/S0010-938X(99)00076-1
  11. S. X. Yu, Q. Y. Lu, J. HAN, Z,-W. Zhang, and Q.-Y. Zhang, J. Rare Earth., 24, 397 (2006). https://doi.org/10.1016/S1002-0721(07)60411-6
  12. D. Andre and J. P. Petitjean, J. Surf. Coat. Technol., 194, 1 (2005). https://doi.org/10.1016/j.surfcoat.2004.05.012