Cobalt-based alloys for orthopaedic applications studied by electrochemical and XPS analysis.
The composition of the passive layers formed by electrochemical oxidation at different passivation potentials on Co-Cr-Mo and Co-Ni-Cr-Mo alloys in simulated physiological solution (SPS), with and without the complexing agent EDTA, was studied by X-ray photoelectron spectroscopy. Composition as a function of depth, cationic fraction and thickness of the passive film was determined. Chromium oxide is shown to be the major constituent of the passive layer on both Co-Cr-Mo and Co-Ni-Cr-Mo alloys. The minor constituents of the passive layers, Co- and Mo-oxide in the case of Co-Cr-Mo alloy and Ni-, Co- and Mo-oxides in the case of Co-Ni-Cr-Mo alloy, are also located in the outer part of the layer. EDTA affects the formation of the passive layer on each alloy. The content of Co-, Ni- and Mo-oxide in the passive layer is lower in the presence of EDTA, thus indicating increased solubility associated with higher stability constants for complexes of metal cations with EDTA.
Kocijan
Aleksandra
A
Jozef Stefan Institute, Department of Physical and Organic Chemistry, Jamova 39, 1000 Ljubljana, Slovenia. Aleksandra.Kocijan@ijs.si
Milosev
Ingrid
I
Pihlar
Boris
B
D000497:Alloys / Q000737:chemistry*; D001826:Body Fluids / Q000737:chemistry*; D002858:Chromium Alloys / Q000737:chemistry; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003343:Corrosion; D004492:Edetic Acid / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods*; D046911:Macromolecular Substances; D008422:Materials Testing / Q000379:methods; D008968:Molecular Conformation; D009983:Orthopedic Equipment; D009985:Orthopedics / Q000379:methods; D010087:Oxides / Q000737:chemistry*; D019736:Prostheses and Implants; D013052:Spectrometry, X-Ray Emission / Q000379:methods*; D013499:Surface Properties; D014800:Vitallium / Q000737:chemistry*
D000497:Alloys; D002858:Chromium Alloys; D020099:Coated Materials, Biocompatible; D046911:Macromolecular Substances; D010087:Oxides; C491689:cobalt-nickel-chromium-molybdenum alloy; D014800:Vitallium; D004492:Edetic Acid