Growth Process and Corrosion Resistance of Ceramic Coatings of Micro-Arc Oxidation on Mg-Nd Magnesium Alloys

Abstract:

The regulation of ceramic coating formed by micro-arc oxidation on Mg-3Nd-0.2Zn-0.4Zr(wt%) magnesium alloys has been investigated by SEM and XRD. The relation of phase structure and corrosion resistance of MgO coating formed by micro-arc oxidation in different growth stages has been analyzed. The results have shown that in the initial stages of micro-arc oxidation, the growth of coating accords with linear regularity, which is the stage of anodic oxidation controlled by electrochemical polarization. With elongated treated time and increased thickness of the coating, the growth of coating accords with parabolic and linear regularity, which is the stage of micro-arc oxidation. In the stage of local arc light, the slope of parabola and thickness of loose coating increases so that the growth rate enhances. The phase structure of loose coating is mainly composed of MgSiO3 and the phase structure of compact ceramic coating is mainly composed of MgO. From the stage of micro-arc oxidation to local arc light, corrosion resistance of coating firstly increase and then decrease. The satisfied corrosion resistance corresponds to the coating time ranging from 7 to15minutes.The addition of rare earth elements in the magnesium alloy reduces the amount of smooth areas on ceramic surface. So the ceramic coating becomes more compact and smooth. The rare earth elements don’t form independent phases in ceramic coating but affect the relative proportion of constitution phases, resulting in the reduction of intermixed magnesium phase and the increase of the MgO and MgSiO₃ phases.

• Periodical: Advanced Materials Research (Volumes 189-193)
• Pages: 891-896
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.189-193.891
• Online since: February 2011
• Authors: Yong Chun Guo, Jian Ping Li, Jin Shan Li, Ping Wang
• Keywords: Corrosion Resistance, Growth Mechanism, Mg-Nd Magnesium Alloy, Micro-Arc Oxidation (MAO)

References

[1] Qing Dong, Liang tao Xiao, Qin Luo. Preparation of Ceramic Membrane by micro arc oxidation on Mg alloy[J]. Materials Science Forum, 2005, 488: 677-679.

DOI: 10.4028/www.scientific.net/msf.488-489.677

[2] Yao hui Liu, Song Li, Lei Pang . Micro-arc Oxidation of AZ91D Diecast Magnesium Alloys in Phosphate Electrolyte[J]. Foundry, 2006, 55（11）：1123-1125.

[3] Jun Liang, Bao gang Guo, Jun Tian . Influence of Process Parameters on Micro-arc Oxidation Coating On AZ91C Magnesium Alloys[J]. Journal of Materials Science & Engineering. 2005, 23（2）：262-264.

[4] Ji hui Wang, Da ran Fang, Jing Yang. Electrolyte Components of Microarc Oxidation for Magnesium Alloy[J]. Journal of Tianjin University, 2005, 38（11）：1026-1028.

[5] Ping Wang, Jian ping Li, Qun Ma. Optimization of Electrolyte Formula of Micro-arc Oxidation for Mg-9Gd-3Y-0. 6Zn-0. 5Zr Magnesium Alloys in Aluminate Solutions[J]. Special Casting and Nonferrous Alloys, 2008, 28(7): 502-503.

[6] M. Laleh, A. Sabour Rouhaghdam, T. Shahrabi, A. Shanghi. Effect of Alumina Sol Addition to Micro-arc Oxidation Electrolyte on the Properties of MAO Coatings Formed on Magnesium Alloy AZ91D[J]. Journal of Alloys and Compounds, 2010, in press.

DOI: 10.1016/j.jallcom.2010.02.098

[7] Allen Bai , Zhi-Jia Chen. Effect of electrolyte additives on anti-corrosion ability of micro-arc oxide coatingsformed on magnesium alloy AZ91D[J]. Surface & Coatings Technology, 2009, 203(1): 1956-(1963).

DOI: 10.1016/j.surfcoat.2009.01.032

[8] Peibo Sua, XiaohongWub, c, Yun Guoc, Zhaohua Jianga. Effects of cathode current density on structure and corrosion resistance of plasma electrolytic oxidation coatings formed on ZK60 Mg alloy[J]. Journal of Alloys and Compounds, 2009, 475(1): 773-777.

DOI: 10.1016/j.jallcom.2008.08.030

[9] R.F. Zhang. Film formation in the second step of micro-arc oxidation on magnesium alloys[J]. Corrosion Science, 2010, 52: 1285-1290.

DOI: 10.1016/j.corsci.2009.12.025

[10] R.F. Zhang a, b, D.Y. Shan a, R.S. Chena, E.H. Hana. Effects of electric parameters on properties of anodic coatings formed on magnesium alloys[J]. Materials Chemistry and Physics, 2008, 107: 356-363.

DOI: 10.1016/j.matchemphys.2007.07.027

[11] Fa he CAO, Long yong LIN, Zhao ZHANG, etal. Environmental friendly plasma electrolytic oxidation of AM60 magnesium alloy and its corrosion resistance[J]. Trans. Nonferrous Met. Soc. China, 2008, 18: 240-247.

DOI: 10.1016/s1003-6326(08)60043-6

[12] Bai ling Jiang, Guo jian Wu, Shu fen Zhang, Ting quan Lei. Research on Micromechanism and Growth Procedure of Ceramic Coating Formed by Micro-arc Oxidation on Magnesium Alloys[J]. Transactions of Materials and Heat Treatment, 2002, 23(1): 6-7.

[13] R.F. Zhang , S.F. Zhang. Formation of micro-arc oxidation coatings on AZ91HP magnesium alloys[J]. Corrosion Science, 2009, 51: 2820-2825.

DOI: 10.1016/j.corsci.2009.08.009

[14] Li chen Zhao, Chun xiang Cui , Qing zhou Wang, Shao jing Bu. Growth characteristics and corrosion resistance of micro-arc oxidation coating on pure magnesium for biomedical applications[J]. Corrosion Science, 2010, in press.

DOI: 10.1016/j.corsci.2010.03.008

[15] Limin Chang. Growth regularity of ceramic coating on magnesium alloy by plasma electrolytic oxidation[J]. Journal of Alloys and Compounds, 2009, 468: 462-465.

DOI: 10.1016/j.jallcom.2008.01.069