Study of formation mechanism of corrosion resistant oxide films and surface oxidation phenomena of magnesium alloys

镁合金耐蚀氧化膜形成机理及表面氧化现象研究

• 批准号: 10650718
• 负责人: ONO Sachiko
• 金额: $ 2.5万
• 依托单位: Chiba Institute of Technology (1999)Shibaura Institute of Technology (1998)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650718/
• 关键词: magnesium alloys; Surface finishing; Anodizing; electropolishing; film structure; electric breakdown; アノード電解挙動; TEM; マグネシウム; 皮膜生成機構; 電界研磨

The practical importance of magnesium has remarkably increased, especially in ecological and environmental points of view. However, no enough information on the microstructure and fundamental growth mechanism of oxide films on magnesium was available. In the present research, formation behavior of anodic films grown on pure magnesium and magnesium alloys was investigated by electrochemical analysis, TEM, SEM and surface analysis such as XPS and GD-OES. Electropolishing of magnesium can be performed successfully to obtain bright surface following the similar mechanism to that of aluminum. When anodic voltage increases to around 5V in alkaline solutions, a current density extensively increases. Further increase in voltage decreases the current until the voltage reaches to a critical voltage of electric breakdown. The critical voltage is dependent on magnesium substrate purity and aluminum content. It increases in the order; 99.6%, AZ31, AZ91 and 99.95%. Including impurities decrease breakdown voltage while aluminum decreases breakdown voltage. When aluminum ions are added in electrolytes the critical voltage also increases. The presence of small amount of aluminum in either substrate or electrolyte improves the film property by selective deposition of spinel (MgAlィイD22ィエD2OィイD24ィエD2) in the oxide film. The cylindrical pore structure and the barrier layer, which are similar to the Keller's model of anodic alumina, are also confirmed by direct cross-sectional observation. After the sealing of anodic film in a boiling solution containing sodium silicate, platelet-like hydroxides in pores, which are similar to sealed anodic films on aluminum, is indicated.

镁的实际重要性显著增加，特别是在生态和环境方面。然而，关于镁表面氧化膜的微观结构和基本生长机制的信息还很少。本研究采用电化学分析、透射电子显微镜、扫描电子显微镜以及XPS、GD-OES等表面分析手段，研究了纯镁及镁合金表面阳极氧化膜的形成行为。镁的电抛光可以成功地获得光亮的表面，其机理类似于铝的抛光机理。在碱性溶液中，当阳极电压增加到5V左右时，电流密度显著增加。电压的进一步增加会降低电流，直到电压达到电击穿的临界电压。临界电压取决于镁衬底纯度和铝含量。依次递增：99.6%、AZ31、AZ91和99.95%。掺杂降低了击穿电压，而铝降低了击穿电压。当铝离子加入到电解液中时，临界电压也会增加。通过在氧化膜中选择性地沉积尖晶石(镁铝ィイD22ィエD2OィイD24ィエD2)，在基片或电解液中加入少量铝改善了氧化膜的性能。直接横截面观察也证实了氧化铝的柱状孔结构和阻挡层，这与Keller的阳极氧化铝模型相似。在含有水玻璃的沸腾溶液中封闭阳极膜后，发现气孔中有片状氢氧化物，类似于铝表面封闭的阳极膜。

项目成果

K.Asami: "Quantitative XPS Characterization of Magnesium Oxidized in Air"J.Electrochem. Soc.. 147, No.4 (in press). (2000)

K.Asami：“空气中氧化镁的定量 XPS 表征”J.Electrochem。

小野幸子: "アノード酸化により生成する多孔質皮膜の構造と成長機構" 表面科学. Vol.19,No.12. 790-798 (1998)

小野幸子：“阳极氧化制备的多孔膜的结构和生长机制”《表面科学》第 19 卷，第 790-798 期（1998 年）。

Sachiko ONO: "Structure and Growth Mechanism of Porous Anodic Oxide Films -Anodizing of Aluminum and Magnesium-"J.Surf Sci. Soc. Jpn.. 19,No.12. 790-798 (1998)

小野幸子：“多孔阳极氧化膜的结构和生长机制-铝和镁的阳极氧化-”J.Surf Sci。

木島,小野,山下,増子: "マグネシウムのアノード電解挙動と酸化皮膜構造"表面技術協会第101回講演大会 講演要旨集. (印刷中). (2000)

Kijima、Ono、Yamashita、Masuko：“镁的阳极电解行为和氧化膜结构”表面技术协会第 101 届会议摘要（2000 年）。

小野幸子: "アノード酸化により生成する多孔質皮膜の構造と成長機構-アルミニウムおよびマグネシウムについて-"表面科学. 19. 790-798 (1998)

小野幸子：“阳极氧化产生的多孔薄膜的结构和生长机制 - 关于铝和镁 -”表面科学 19. 790-798 (1998)。