Using the additives to modify the anti-corrosion ability of oxide coating on AZ91D Alloy

• Main Authors: CHEN, JHIH-JIA, 陳志嘉
• Other Authors: Allen bai
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/49553565651529609490

碩士 === 高苑科技大學 === 高分子環保材料研究所 === 96 === Abstract This study Examined the optimal electrolyte composition oxident coating on magnesium alloys AZ91D by micro-arc oxidation method to improve corrosion resistance . The chemicals stadied in this work includes sodium hydroxide, sodium silicate, sodium borate, and hexamethylenetetramine (HMTA). The oxide coating of AZ91D alloy was analyzed by SEM, X-ray, thickness, corrosion testing, and CV to find an optimum condition for plating oxide coating with high corrosion resistance. The results showed that all the additives provide high cortosion resistance coating on AD91Z alloy. For example, the electrolyte with sodium silicate 10 g/L, sodium hydroxide 45 g/L, sodium boriate 10 g/L, and hexamethylenetetramine (HMTA) 15 g /L form high corrosion resistance oxdnt coating. Moreover, the corrosion resistance of the oxide at coating reach the highest value when the N,N,N',N'-Tetramethylethylenediamine was added in the electrolyte 0.04A/cm2 . The anodizing condition of breakdown voltage is 200 V and plating temperature at 25°C. According to X-ray scattering anlalysis, main composition inoxide coating include MgO and Mg, MgAl2O4, Mg2SiO4. According to the results of tafel measurement, the intensity of MgO crystalline peak increases with the increasing corrosion resistance of oxide coating on AD91D alloy. By SEM results, these additives modify the surface of oxide coating on AZ91D alloy by form a smooth layer without cracks and holes. Sodium borate was used in electrolyte during micro-arc oxidation process to increase sodium content for improving the corrosion abiltiy of oxide coating on AZ91D. In addition, Hexamethylenetetramine (HMTA) was used to repair those cracks and holes on AZ91D alloy.