Wei-ping Li, Xi-mei Wang, Li-qun Zhu, and Wen Li, Formation mechanism of an aluminium-based chemical conversion coating on AZ91D magnesium alloy, Int. J. Miner. Metall. Mater., 17(2010), No. 5, pp. 641-647. https://doi.org/10.1007/s12613-010-0368-7
Cite this article as:
Wei-ping Li, Xi-mei Wang, Li-qun Zhu, and Wen Li, Formation mechanism of an aluminium-based chemical conversion coating on AZ91D magnesium alloy, Int. J. Miner. Metall. Mater., 17(2010), No. 5, pp. 641-647. https://doi.org/10.1007/s12613-010-0368-7
Wei-ping Li, Xi-mei Wang, Li-qun Zhu, and Wen Li, Formation mechanism of an aluminium-based chemical conversion coating on AZ91D magnesium alloy, Int. J. Miner. Metall. Mater., 17(2010), No. 5, pp. 641-647. https://doi.org/10.1007/s12613-010-0368-7
Citation:
Wei-ping Li, Xi-mei Wang, Li-qun Zhu, and Wen Li, Formation mechanism of an aluminium-based chemical conversion coating on AZ91D magnesium alloy, Int. J. Miner. Metall. Mater., 17(2010), No. 5, pp. 641-647. https://doi.org/10.1007/s12613-010-0368-7
Key Laboratory of Aerospace Materials and Performance (Ministry of Education of China), School of Materials Science and Engineering, Beihang University, Beijing, 100083, China
An environmentally clean aluminium-based conversion coating on AZ91D magnesium alloy was studied in aluminium nitrate solutions. The morphology, composition, structure, and formation mechanism of the coating were investigated in detail using scanning electron microscopy/energy dispersion spectrometry, X-ray diffraction, transmission electron microscopy, and electrochemical corrosion tests. The results show that the conversion coating is composed of magnesium, aluminium, and oxygen, and shows an amorphous structure. In the initial stage of coating formation, the grain-like nucleus is composed of Al10O15·xH2O, (Al2O3)5.333, Al2O3, AlO(OH), MgAl2O4, (Mg0.88Al0.12)(Al0.94Mg0.06)2O4, and (Mg0.68Al0.32)(Al0.84Mg0.16)2O4. The conversion coating formed in the 0.01 mol/L aluminium nitrate solution for 15 min can improve the corrosion resistance of the magnesium alloy greatly. The discussion reveals that the possible formation mechanism for the aluminium-based conversion coating is the reduction reaction on micro-cathodic sites due to the electrochemically heterogeneous magnesium alloy substrate.
Key Laboratory of Aerospace Materials and Performance (Ministry of Education of China), School of Materials Science and Engineering, Beihang University, Beijing, 100083, China
An environmentally clean aluminium-based conversion coating on AZ91D magnesium alloy was studied in aluminium nitrate solutions. The morphology, composition, structure, and formation mechanism of the coating were investigated in detail using scanning electron microscopy/energy dispersion spectrometry, X-ray diffraction, transmission electron microscopy, and electrochemical corrosion tests. The results show that the conversion coating is composed of magnesium, aluminium, and oxygen, and shows an amorphous structure. In the initial stage of coating formation, the grain-like nucleus is composed of Al10O15·xH2O, (Al2O3)5.333, Al2O3, AlO(OH), MgAl2O4, (Mg0.88Al0.12)(Al0.94Mg0.06)2O4, and (Mg0.68Al0.32)(Al0.84Mg0.16)2O4. The conversion coating formed in the 0.01 mol/L aluminium nitrate solution for 15 min can improve the corrosion resistance of the magnesium alloy greatly. The discussion reveals that the possible formation mechanism for the aluminium-based conversion coating is the reduction reaction on micro-cathodic sites due to the electrochemically heterogeneous magnesium alloy substrate.
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