Effect of Water/Alkoxide Molar Ratio on the Synthesis Process and Electrochemical Behavior of Yttria-doped Zirconia Sol-gel Films

The aim of this work is to synthesize and investigate the performance of yttria-doped zirconia solgelcoatings in the chemical corrosion prevention of zircaloy-4 (zirconium alloy) in a 1 N H2SO4environment. The influence of four different molar ratios of water to alkoxide, namely 1, 4, 12, and20, on the coating quality and its corrosion prevention performance was investigated. Differentialthermal analysis and thermogravimetric analysis (DTA-TG) revealed the coating formation process.Surface morphology was examined using scanning electron microscopy (SEM). Microscopicfeatures were obtained by employing energy dispersive spectroscopy (EDX) and X-ray diffraction(XRD). Wet corrosion performance was evaluated by using potentiodynamic polarization andelectrochemical impedance spectroscopy (EIS) techniques. The EDX results approved that theamount of the yttria doped in zirconia was about 8 wt.%. The XRD results showed that thecrystallization of zirconia started near 400 °C. The SEM results showed that denser cracks wereformed at a water/alkoxide molar ratio of 4. The electrochemical tests revealed that, as the molarratio of water to alkoxide was increased beyond 4, the coating quality was damaged and the bestprotection performance was achieved at a water/alkoxide molar ratio of 4.

Keywords:

Sol-gel , Yttria-stabilized Zirconia (YSZ) Coating , Hydrolysis , Crack-free Coating , Corrosion Performance , Yttria-doped Zirconia Coating