鎂合金低污染陽極表面處理技術研究

• Main Authors: Chin-Lung Chang, 張進龍
• Other Authors: Ming-Der Ger
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/78292959143816423308

碩士 === 國防大學中正理工學院 === 應用化學研究所 === 92 === In this study, an anodizing film was formed to protect the magnesium alloy from corrosion. The optimum formula of anodizing solution is obtained through the Taguchi orthogonal design and the corrosion resistance and texture of anodizing film on the magnesium alloy are examined by EIS, SEM and TEM, respectively. It has been shown that the concentrations of silicate, citrate, NaOH and phosphate in the anodizing bath are major factors affecting the corrosion protecting capability of anodizing film. Our results reveal that the optimum formula is as followed: 60 g/L of silicate, 80 g/L of citrate, 70 g/L of NaOH and 20 g/L of phosphate in the anodizing bath. When compared with the plate anodized with dc current, the anodizing film made by using a pulse current improved the impedance resistance substantially. It is found that the optimum operation parameters are as followed: the bath temperature is15℃, the current density is1.6 A/dm2, the frequency is 1000Hz, the duty cycle is 0.3 and treatment time is 15 min. The anodic film shows a two-layer structure consisting of a dense inner layer and a porous outer layer. The TEM diagram showed a number of crystalline particles, which were recognized as MgO by electron diffraction pattern, existing in the Mg matrix were seen. The anodic film is mainly composed of two oxide phases, namely, MgO and Mg2SiO4 identified by X-ray powder diffraction. Based on our results, a possible mechanism of the formation of the anodic film is proposed.