Electrochemical Studies and XPS Analysis of the Surface of Zirconium-702 in Concentrated Nitric Acid With and Without Fluoride Ions
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Zirconium exhibited pseudo-passive behavior in fluorinated nitric acid (11.5 M HNO3 + 0.05 M NaF) as the current density measured from the electrochemical studies was several orders higher than the value in fluoride free nitric acid. Impedance studies on zirconium sample exposed in 11.5 M HNO3 for 240 h confirmed the formation of the passive film with high polarization resistance value and the calculated thickness of the film based on the capacitance value was about ~4.5 nm. On the other hand, in fluorinated nitric acid, the charge transfer resistance value associated with the zirconium dissolution process was dominant when compared to that of the film formation. Results of X-ray photoelectron spectroscopic investigations upheld the presence of ZrOF2 and ZrF4 and indicated that the protective oxide layer growth was restricted by the presence of fluoride ions.
KeywordsZirconium Nitric acid Fluoride Corrosion EIS XPS
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