Abstract
Corrosion products generated in artificial pits of zirconium were characterized in–situ by synchrotron X-ray diffraction and X-ray absorption near edge structure (XANES) 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 farther 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.
Highlights
Zr is an element that is a common constituent of alloys used to manufacture biomedical implants.[1,2] Zr has been used in Ti-alloys to provide improved mechanical properties for surgical implants such as increased strength, e.g. Ti-5Zr,[3,4] or lower Young’s modulus, e.g. Ti-3Zr-13Nb,[5,6] Ti-20Nb-10Zr-5Ta7 and Ti-12Mo-6Zr-2Fe.[8]
The structure and speciation of corrosion products formed on dissolving Zr surfaces in simulated physiological solutions were characterized in-situ by synchrotron X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES), and the morphology and size of ex-situ corrosion products was determined with TEM
Overall structure of corrosion products.—Figure 2a shows an optical image of a ∼3 mm deep Zr artificial pit that was grown at 0.8 V (Ag/AgCl) in physiological saline (0.9% NaCl) solution with addition of 0.1% H2O2 and 4% albumin
Summary
Zr is an element that is a common constituent of alloys used to manufacture biomedical implants.[1,2] Zr has been used in Ti-alloys to provide improved mechanical properties for surgical implants such as increased strength, e.g. Ti-5Zr,[3,4] or lower Young’s modulus, e.g. Ti-3Zr-13Nb,[5,6] Ti-20Nb-10Zr-5Ta7 and Ti-12Mo-6Zr-2Fe.[8]. A number of Zr-based glass forming alloys have been described and offer the possibility of improved mechanical properties and chemical stability.[12,13,14]. Zr is susceptible to pitting attack, especially in halide ion containing environments.[15,16] a number of studies have shown the pitting susceptibility of Zr-based alloys including metallic glasses in chloride–containing simulated physiological solutions.[14,17] If implants in the body undergo pitting, free metal ions and other corrosion products may be released into the surrounding tissue where they can stimulate adverse biological reactions.[18,19] There is increasing concern over the long-term health effects of corrosion product accumulation in peri-implant tissue. The reservoir contained a Ag/AgCl reference electrode, a Pt wire counter electrode
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