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Open AccessArticle

One-Step Fabrication and Localized Electrochemical Characterization of Continuous Al-Alloyed Intermetallic Surface Layer on Magnesium Alloy

1,†, 1,†, 1, 2, 3, 3, 2,3 and 2,3,*
1
State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China
2
Key Laboratory of Advanced Ceramics and Machining Technology (Ministry of Education), School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China
3
Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Coatings 2018, 8(4), 148; https://doi.org/10.3390/coatings8040148
Received: 2 March 2018 / Revised: 7 April 2018 / Accepted: 8 April 2018 / Published: 18 April 2018
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Abstract

A continuous intermetallic compound coating was fabricated on AZ91D magnesium alloy via heat treatment at 400 °C in AlCl3-NaCl molten salts for 10 h. The microstructure and composition of the coating were characterized by scanning electron microscope and energy dispersive X-ray spectrometry. The results showed that the coating has a two-layer structure (the outer Mg2Al3 phase layer and the inner Mg17Al12 phase layer) up to 37 μm thick with compact and planar interfaces between the layers and the substrate. The corrosion property of the coating was investigated using electrochemical impedance spectroscopy (EIS) and two localized electrochemical techniques, i.e., localized electrochemical impedance spectroscopy (LEIS) and scanning vibrating electrode technique (SVET). The charge transfer resistance (Rct) of the Al-alloyed coating was 2119 Ω cm2. The localized impedance and current density maps obtained through LEIS and SVET indicate not only significantly improved corrosion resistance (the impedance modulus increased by one order of magnitude and the current density decreased to approximately 3.8%, compared with the substrate) but also defect-free surface condition. View Full-Text
Keywords: magnesium alloy; intermetallic coating; molten salt; localized electrochemical analysis; corrosion magnesium alloy; intermetallic coating; molten salt; localized electrochemical analysis; corrosion
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Fu, Z.; Chen, X.; Liu, B.; Liu, J.; Han, X.; Deng, Y.; Hu, W.; Zhong, C. One-Step Fabrication and Localized Electrochemical Characterization of Continuous Al-Alloyed Intermetallic Surface Layer on Magnesium Alloy. Coatings 2018, 8, 148.

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