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The Electrochemical Properties and Mechanism of Formation ofAnodic Oxide Films on Mg-Al Alloys
김성종,MasazumiOkido 대한화학회 2003 Bulletin of the Korean Chemical Society Vol.24 No.7
The electrochemical properties and the mechanism of formation of anodic oxide films on Mg alloys containing 0-15 mass% Al, when anodized in NaOH solution, were investigated by focusing on the effects of anodizing potential, Al content, and anodizing time. The intensity ratio of Mg(OH)₂ in the XRD analysis decreased with increasing applied potential, while that of MgO increased. Mg(OH)₂ was barely detected at 80 V, while MgO was readily detected. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. The intensity ratio of the β phase increased with aluminum content in Mg-Al alloys. During anodizing, the active dissolution reaction occurred preferentially in β phase until about 4 min, and then the current density increased gradually until 7 min. The dissolution reaction progressed in α phase, which had a lower Al content. In the anodic polarization test in 0.017 mol· dm −3 NaCl and 0.1 mol· dm −3 Na₂SO₄ at 298 K, the current density of Mg-15 mass% Al alloy anodized for 10 min increased, since the anodic film that forms on the α phase is a non-compacted film. The anodic film on the α phase at 30 min was a compact film as compared with that at 10 min.
최윤일,Kensuke Kuroda,MasazumiOkido 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.5
The effects of solution temperature on the initial corrosion characteristics of wrought AZ61 and die-cast AZ91D Mg alloys in 0.1M NaCl were analyzed. Systematic studies indicate that AZ91D exhibits higher corrosion resistance than AZ61 at room temperature. However, at high temperatures of around 55 °C, we observed contradictory corrosion behavior, as demonstrated by cyclic corrosion tests and electrochemical tests including potentiodynamic polarization, potentiostatic polarization, and elecrochemical impedance spectroscopy. As a result, AZ61 rather showed higher corrosion resistance from the point of view of pit initiation during the immersion at 55 °C resulting from the strengthening of surface passivation. These results can be attributed to the microstructure of AZ61 which contains sub-micron scale β-phase particles dispersed effectively within the α-Mg grains whereas AZ91D has many α-Mg that do not containing any β-phases.