Mechanism of Corrosion Protection of Magnesium Alloys Anodized by Phosphate Electrolyte
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- Murakami Koji
- Industrial Technology Research Institute of Okayama Prefectural Government
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- Hino Makoto
- Industrial Technology Research Institute of Okayama Prefectural Government
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- Nakai Kiyomichi
- Graduate School of Science and Engineering, Ehime University
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- Kobayashi Sengo
- Graduate School of Science and Engineering, Ehime University
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- Saijo Atsushi
- Hori Metal Finishing Industry Co., Ltd.
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- Kanadani Teruto
- Faculty of Engineering, Okayama University of Science
Bibliographic Information
- Other Title
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- りん酸塩電解液による陽極酸化処理を施した各種マグネシウム合金の防食機構
- リンサンエン デンカイエキ ニ ヨル ヨウキョク サンカ ショリ オ ホドコシタ カクシュ マグネシウム ゴウキン ノ ボウショク キコウ
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Abstract
Corrosion resistance of anodized surfaces on high-purity magnesium (99.95 mass%), rolled sheets of ASTM AZ31B (Mg-2.9Al-0.85Zn) magnesium alloy and die-cast plates of ASTM AZ91D (Mg-9.1Al-0.75Zn) magnesium alloy has been studied. Anodization was conducted by environment-friendly electrolysis whose electrolyte consists of phosphate and ammonium salt. The anodized surface was covered with amorphous film, and showed only discoloration during salt spray test where formation of corrosion product (magnesium hydroxide) was well suppressed within 605 ks. Even when the anodized surfaces were trenched with ceramic knife to form locally exposed substrate, corrosion was well suppressed by formation of new type of dense protective films for each substrate which consist of oxygen, magnesium, aluminum and phosphorus. Anodic polarization curves indicate that the anodized surfaces show sacrificial function due to the thermodynamically unstable state of phosphorus in the anodized layers and its resulting release of electrons. From the viewpoint of kinetics in corrosion on the anodzed surfaces, the curves show that the anodized layers dissolve quite slowly into the electrolyte compared with the case of the untreated substrates. The excellent corrosion protection obtained by the anodization is considered to be based on the formation of a dense protective film on the exposed area, as well as sacrificial function of the amorphous anodized layer.<br>
Journal
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- Journal of the Japan Institute of Metals and Materials
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Journal of the Japan Institute of Metals and Materials 73 (5), 354-361, 2009
The Japan Institute of Metals and Materials
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Details 詳細情報について
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- CRID
- 1390282681455353088
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- NII Article ID
- 10024818620
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- NII Book ID
- AN00187860
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- ISSN
- 18806880
- 24337501
- 00214876
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- NDL BIB ID
- 10297712
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- Text Lang
- ja
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- Data Source
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- JaLC
- NDL
- Crossref
- CiNii Articles
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- Abstract License Flag
- Disallowed