Reactivity of the surface of zirconium during pickling in nitric‐hydrofluoric acid

Abstract

The behaviour of zirconium in hydrofluoric-nitric acid pickling solutions has been studied using electrochemical methods, X-ray diffraction and Raman spectrometry. During a pickling experiment the depletion of the solutions could be correlated with the consumption of hydrofluoric acid to form metal 0x0-or oxofluorocomplexes.The role of nitric acid added to the hydrofluoric acid for pickling has been discussed after replacing it by other strong acids or by hydrogen peroxide. It appears that the zirconium dissolution rate only depends on the hydrofluoric acid concentration, but that the properties of the oxide film are determined by the nature of the ' strong acid added to HF, it can be assumed that metal dissolution occurs through the oxide film and that ionic diffusion through the film is a rate determining step.