The Improvement of Electrolytic Deposition of ZrO2 Thin Film on

• Main Authors: Cheng, Ta Huang, 鄭達煌
• Other Authors: S. K. Yen
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/51118955938684479468

碩士 === 國立中興大學 === 材料工程學研究所 === 85 === In this research, SUS 316L stainless steel was electrolytically deposited with zirconia (ZrO2) coating in an aqueous solution of zirconyl nitrate [ZrO(NO3)2]. By controlling electrochemical and sintering parameters, the characteristics of the coating were investigated. Through cathodic polarization experiments, it was found that the better potential of deposition was in the diffusion limit current iL of H+ concentration polarization of the cathodic polarization curves. At more negative potential, hydrogen bubbles were found on the specimen surface. Also the deposition rate is increased with the concentration of solution increased, but without good uniformity. In addition, a much longer deposition time made Zr( OH)4 gel film produce obvious crack after drying, but a proper deposition time did not. The XRD and TEM analysis showed that : (A) Preferred orientation of monoclinic (-1 1 1) plan of the coating deposited on 316L stainless steel was found at T≦ T7. It is considered as the chemical bonds effect between substrate and crystallized zirconia. (B) At T≦T7, a monoclinic phase was detected at first, then a tetragonal phase appeared and coexisted with a monoclinic phase, at last the tetragonal phase completely replaced the monoclinic phase. At different temperature, the time for phase formation and phase transformation was decreased with the temperature increased. Dynamic polarization tests in 0.6M NaCl showed that specimens with properly sintered zirconia coating (such as T2-T4 and so on) can improve corrosion resistance, which showed the higher pitting potential (Epit) and protection potential (Eprot) than the as-deposited specimen. Also, the pitting density is lower and shallower.