STUDY OF THE EFFECT OF THERMAL TREATMENTS ON THECORROSION BEHAVIOUR OF CoCrMo ALLOY USINGELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS)

摘要

CoCrMo alloys are one of the most important biomaterials for orthopaedic applications,rnwidely used in total joint replacements. The thermal treatments applied to CoCrMo alloysrn(as-cast, annealing solution, hot isostatic pressing or sintered for porous coating) modifies thernmicrostructure of the alloy and change the electrochemical and mechanical properties of thernbiomaterial. Thus, the aim of this work is to characterize the electrochemical behaviour ofrnCoCrMo alloys depending on the thermal treatment (changes in the microstructure) and thernsolution chemistry (in simulated body fluids).rnMetallographic studies, Open Circuit Potential (OCP) measurements, potentiodynamicrncurves, potentiostatic measurements and Electrochemical Impedance Spectroscopy (EIS) arernemployed to characterize the CoCrMo alloy after three different thermal treatments inrnsimulated body fluids (bovine serum, saline solution and saline solution with 0.5 g/l ofrnalbumin).rnThe study reveals that the properties of the passive layer depend on the thermal treatment andrnthe chemistry of the simulated body fluid. EIS results show that the resistance of the passivernlayer increased with the solubilization of carbides in bovine serum. On the other hand, thernalbumin acts as cathodic inhibitor and accelerates the anodic reaction in all cases.