In-situ Synchrotron X‑ray Characterisation of Corrosion Products in Zr Artificial Pits in Simulated Physiological Solutions

Abstract

Corrosion products generated in Zirconium artificial pits were characterised in‑situ by synchrotron X‑ray diffraction and XANES (X‑ray absorption near edge structure) in physiological saline, with and without addition of 4% albumin and/or 0.1% H2O2. Zr metal fragments and tetragonal ZrO2 particles were detected in aggregated black corrosion products away from the corrosion front. At the corrosion front, a ZrOCl2  8H2O salt layer of a few hundreds of microns thickness was formed. Coarsened ZrOCl2  8H2O crystallites were found further out into the solution. The Zr solution species were confirmed to be in a tetravalent state by XANES. TEM imaging of the corrosion products revealed heterogeneity of the morphology of the Zr metal fragments and confirmed their size to be less than a few microns. The formation and speciation of Zr corrosion products were found not affected by the presence of H2O2 and/or albumin in physiological saline. Furthermore, bulk Zr electrochemistry identified that the presence of H2O2 and/or albumin did not affect passive current densities and pitting potentials of the bulk Zr surface. Therefore, it is concluded that the pitting susceptibility and pit chemistry of Zr in physiological saline were unaffected by the presence of H2O2, albumin or their combinations.