AZ31 Mg합금의 PEO피막 형성거동에 미치는 인산나트륨 농도의 영향
Effect of Na3PO4 Concentration on The Formation Behavior of PEO films on AZ31 Mg Alloy
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Formation behavior of PEO (Plasma Electrolytic Oxidation) films on AZ31 Mg alloy was investigated under application of 310 Hz AC as a function of Na3PO4 concentration from 0.02 M to 0.2 M. Film formation voltage and in-situ observation of arcs generated on the specimen surface were recorded with time, and surface morphologies of the PEO films were investigated using optical microscopy, confocal scanning laser microscopy and scanning electron microscopy. PEO film formation voltage decreased linearly with increasing Na3PO4 concentration which is attributed to the increase of solution pH. PEO films were grown uniformly over the entire surface in Na3PO4 solutions between 0.05 M and 0.1 M. However, non-uniform PEO films with white spots were formed in Na3PO4 solutions containing more than 0.1 M. Thickness and roughness of PEO films on AZ31 Mg alloy increased linearly with increasing Na3PO4 concentration and their increasing rates appeared to be much higher under 1 M than above 1 M. The experimental results suggest that phosphate ions can contribute to the formation of PEO films but higher Na3PO4 concentration more than 1 M results in local damages of PEO films due to repeated generation of white arcs at the same surface site of AZ31 Mg alloy.
Abstract
Formation behavior of PEO (Plasma Electrolytic Oxidation) films on AZ31 Mg alloy was investigated under application of 310 Hz AC as a function of Na3PO4 concentration from 0.02 M to 0.2 M. Film formation voltage and in-situ observation of arcs generated on the specimen surface were recorded with time, and surface morphologies of the PEO films were investigated using optical microscopy, confocal scanning laser microscopy and scanning electron microscopy. PEO film formation voltage decreased linearly with increasing Na3PO4 concentration which is attributed to the increase of solution pH. PEO films were grown uniformly over the entire surface in Na3PO4 solutions between 0.05 M and 0.1 M. However, non-uniform PEO films with white spots were formed in Na3PO4 solutions containing more than 0.1 M. Thickness and roughness of PEO films on AZ31 Mg alloy increased linearly with increasing Na3PO4 concentration and their increasing rates appeared to be much higher under 1 M than above 1 M. The experimental results suggest that phosphate ions can contribute to the formation of PEO films but higher Na3PO4 concentration more than 1 M results in local damages of PEO films due to repeated generation of white arcs at the same surface site of AZ31 Mg alloy.
참고문헌 (18)
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