| Summary: | 碩士 === 高苑科技大學 === 化工與生化工程研究所 === 97 === The anti-corrosion ability, morphology, microstructure and hardness performance of oxide coatings anodized on AZ91D alloy using micro-arc oxidation techniques at different current density was investigated within this study. It found that the micro-arc oxidation process improved the morphology, hardness, thickness and corrosion resistance of an oxide coating, which are connected with changes in behavior of current density to form spark discharges through a micro-arc oxidation process.
In the SEM results, the constant current density, 0.02 A/cm2, was used to produce the homogeneous spark discharge for smoothing the surface of an oxide coating. The homogeneous spark discharge leads the lower thermal stress. Then, the anti-corrosion ability of an oxide coating was improved. Moreover, the same trend was also found in the Tafel examination.
Finally, the optima condition to prepare the oxide coating with the better anti-corrosion ability is that the electrolyte composed of sodium borate 0.06M, tetramethylethylenediamine 0.18M, sodium silicate 0.04M, and NaOH 2M. In addition, the oxide coating has the passive potential of -1.0V~0.2V and corrosion current density of 3.16×10-3 A/cm2 in the Tafel examination.
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