The Study of the Reaction Models of Electrochemical Anodic Dissolution

• Main Authors: Yi-Ho Chen, 陳貽和
• Other Authors: Shuo-Jen Lee
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/70734019366838642856

博士 === 元智大學 === 機械工程學系 === 101 === Electroplishing (EP) technology and its reaction models were proposed by Jacquet, Tegart and Hoar in 1930’s and 1940’s. After 1950’s, most of the EP researches focused on specific metal in a specific electrolyte or its process parameter optimization. In literatures, there are a lot of contradictions. The old reaction models could not explain some of the phenomena in EP. Therefore, re-evaluation and building innovative reaction models of EP process are the goal of this study. Electrochemical anodic dissolution reaction has two important characteristics for surface engineering. The first is the formation of surface morphology. The second is the change of surface chemical composition. In this study, the surface morphology changes in EP are observed and the bubbles are identified as the key factor that affects the formation of surface morphology. Using the COMSOL Multi-Physics commercial software, the effects of bubbles in EP reaction could be simulated and evaluated. Hence, the Bubble Shielding Effect (BSE) and the Broken Bubble Tunnelling Effect (BBTE) were proposed. These two effects explain the surface roughness limitation and the formation of pitting holes in EP. The model of surface morphology formation is established. Some confirmation tests were carried out to verify the model. The surface chemical composition analysis uses XPS to detect the amount of Cr, Fe, and oxygen atoms on the electropolished surface under different process parameters such as current density, applied electric voltage, electrolyte, and temperature. High Cr/Fe ratio and thick Cr2O3 are the goal of the study. Finally, the process parameters of EP were optimized and the Cr/Fe ratio reached around 1.75 to 2. The results are much higher than the requirement of the Cr/Fe ratio of 1.5 in SEMASPEC “Test Method for XPS Analysis of Surface Composition and Chemistry of Electropolished Stainless Steel Tubing for Gas Distribution System Components.”