The forming mechanism discussion of Cr+3 chemical conversion coating on non-cyanide galvanization

• Main Authors: Wen, Niann-Tsyr, 文念慈
• Other Authors: Ger, Ming-Der
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/36794653042629135825

博士 === 國防大學中正理工學院 === 國防科學研究所 === 97 === Discussing the mechanism of the trivalent chromium conversion coating growth was the main work of this research. It included the character analysis of the formula of the treatment solution, the operating condition of the film growth and aftertreatment, and different type trivalent chromium coatings. The initial period, according by the electrochemistry and the material analysis, understood the role of ingredients in the high temperature (60℃) trivalent chromium conversion treatment for the coating forming, and the composition, structure influence for the coating character. Demonstrated by the experimental result that, trivalent chromium conversion coating had three-layers structure, and the coating existence instability were related with this three layers which owned there different composes. The film was able to improve stability by roasting 90℃,30min. Next, according by the empirical datum accumulation, deduced the trivalent chromium conversion coating growing mechanism and the anticorrosion reason. Both the redox reaction and deposit reaction governed the coating growth. The former was happened at boundary layer from inside to outside to grow the film, and the latter was from outside to inside to pile up one on surface layer. The corrosion resistance mainly was provided by the boundary layer which rich zinc content. Finally, because of mechanism commanding, accelerating the zinc oxide and changing the chromium content to be more than the zinc content across the film, successfully designs a high corrosion resistance trivalent chromium coating in normal temperature (35℃) production. Moreover, puts the Si element into the film to promote the heat-resisting nature, simultaneously.