Influence of Some Parameters on Passivation of Zirconium and the Stability of the Anodic Oxide Film

Passivation of the zirconium surface and stability of anodic oxide film were investigated as a function of surface preparation. The mechanically polished surface appeared to be more reactive toward oxide thickening than the etched one, as revealed by impedance measurements. Oxide film formed on the etched electrode dissolved faster than that formed on the mechanically polished one. This was attributed to the increase of structural defects within the oxide film formed on the etched surface. Dissolution of the anodic oxide film as a function of pretreatment conditions and cathodic pulsing also was studied. Leaving the oxide film in air or immersing it in water caused a decrease in the dissolution rate of the outer layer. Increasing the cathodic charge through the anodically formed oxide film led to an increase in the dissolution rate of its outer layer.