Electrochemical Surface Treatment of Magnesium Alloys
| Autor: | Yuan-Ming Chen, 陳遠銘 |
|---|---|
| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 Effects of electrolyte composition, pH, potential and reaction time applied during anodizing, corrosion of anodic films formed on AZ91D magnesium alloy were investigated in this study. Corrosion potential of Mg alloy was examined by current-potential relationship. Microstructures of Mg alloy and anodic film were examined by optical microscopy; the gloss of anodic film was determined by gloss meter; the surface roughness of anodic film was determined by surface roughness tester and atomic force microscope (AFM). Protection of anodized film was evaluated by electrochemical impedance spectroscopy (EIS). The results showed that the concentration of hydrogen ion of electrolyte and temperature increased with increasing corrosion current. Addition alcohol was decreasing corrosion current. Change in the ratio of phosphoric-alcohol and application of ultrasonic vibration increasing corrosion current. In alkaline solutions containing 1 M NaOH, the gloss of Mg alloy could increase. In alkaline system, effects of grinding by sandpaper, anodizing potential and reaction duration on surface roughness of Mg alloy were investigated. The results showed the surface roughness of the specimens treated by grinding and 2 V anodizing was best. The surface roughness of specimens without grinding also improved with increased reaction duration. The corrosion resistance of the anodized AZ91D Mg alloy in 3.5 wt.% NaCl solution was evaluated by electrochemical impedance spectroscopy (EIS). Anodized AZ91D Mg alloy at 1 V for 60 min exhibited better corrosion resistance than that at 1 V for 10 min. Higher corrosion resistance was also found for Mg alloy anodized at 2 V than that at 1 V. Even a better result could be obtained after sealing with hot water. The optimal parameter of electrochemical treatment was obtained via the Taguchi orthogonal design. Using optimal parameters could improve gloss by 19.40% and surface roughness by 23.7%. Furthermore, the design proved that applied potential was the key parameter. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|