Crystallization of a chemical conversion layer that forms on AZ91D magnesium alloy in carbonic acid

This investigation studied the crystallization of a chemical conversion layer that formed on AZ91D Mg alloy in carbonic acid. The layer was an amorphous precursor to a crystalline Mg-Al layered double hydrotalcite, which improved the corrosion resistance of the alloy. The precursor must be treated w...

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Bibliographic Details
Published in:Corrosion Science
Main Authors: Lin, Jun-Kai, Jeng, Kai-Li, Uan, Jun-Yen
Other Authors: National Chung Hsing University,Department of Materials Engineering, 國立中興大學材料工程學系, Miao-zhen Luo
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier Ltd. 2011
Subjects:
A. Magnesium
A. Acid solutions
B. Polarization
B. IR spectroscopy
B. Raman spectroscopy
C. Amorphous structures
Carbonic acid
Online Access:http://hdl.handle.net/11455/43182
https://doi.org/10.1016/j.corsci.2011.07.035
Description
Summary:This investigation studied the crystallization of a chemical conversion layer that formed on AZ91D Mg alloy in carbonic acid. The layer was an amorphous precursor to a crystalline Mg-Al layered double hydrotalcite, which improved the corrosion resistance of the alloy. The precursor must be treated with a strongly alkaline solution, causing the leaching out of amphoteric Al3+. The leaching step evidently caused crystallization from an amorphous precursor layer to a crystalline coating. Nuclear magnetic resonance analysis indicated that Al3+, which was originally randomly coordinated with surrounding OH− in the precursor, coordinated octahedrally with OH− groups in the crystalline conversion coating.

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