Optimization of Anodizing Condition for Mg-14mass%Li-3mass%Al Alloy

Abstract:

Mg-Li system alloys also has excellent cold-workability compared to commercial hcp-structured Mg alloys. However, Mg-Li alloys have poor corrosion resistance because not only that is Mg-based alloy but Li as a major alloying element is a less noble metal. For example, Mg-Li alloy sheet indicates high corrosion rate and exfoliation corrosion as a result of long-term corrosion test. The authors reported Mg-14 mass%Li-3 mass%Al alloy has the highest corrosion resistance in β-type solid solution alloy. Even though the optimized alloy composition, the alloy does not have enough corrosion resistance for practical use. In this study, anodized coating on Mg-Li alloy using phosphate solution was investigated. Anodizing of Mg-Li alloy facilitates the dissolution of substrate because of high Li concentration in this alloy. Therefore, the anodizing conditions were widely examined. As a result, the coating with approximately 15-20 μm of the surface layer was successfully formed. The surface layer was composed of MgAl₂O₄ and some phosphorus compounds. The thickness of anodized layer varied with the anodizing conditions. The dense surface layer was formed at a certain anodizing voltage and the corrosion resistance of anodized Mg-Li alloys was improved. However, the surface has some cracks and large flaky compounds. The formation mechanism of dense layer during anodizing were discussed.

• Periodical: Materials Science Forum (Volume 1106)
• Pages: 9-13
• DOI: https://doi.org/10.4028/p-1nNrQR
• Online since: December 2023
• Authors: Taiki Morishige*, Satoki Takiyama, Yuka Ichigi, Toshihide Takenaka
• Keywords: Anodizing, Corrosion Resistance, Magnesium Alloy, Mg-Li Alloy, Surface Coating

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