Influence of the surface mechanical attrition treatment (SMAT) on the corrosion behavior of Co28Cr6Mo alloy in Ringer’s solution

Abstract : The low carbon Co28Cr6Mo alloy used for artificial joints like hip and knee prostheses is subjected to a surface treatment called SMAT (surface mechanical attrition treatment). The purpose of this treatment is to modify the surface mechanical properties of the treated alloy. Since the SMAT impacts the surface of materials, its influence on the corrosion behavior of the CoCrMo alloy has to be assessed in a physiological solution as Ringer’s solution. Furthermore, a specific biomedical polishing is coupled with the SMAT in order to finalize the production of a hip prosthesis ready for use. The corresponding corrosion behavior is also studied. The corrosion behavior of CoCrMo alloy samples is investigated using electrochemical techniques (potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS)) in physiological liquid and simulated by an equivalent circuit. The polarization results show the reduction of the corrosion current density and the increase of the corrosion potential after the SMAT. The EIS analyses also show the benefit of the SMAT on the corrosion resistance of the CoCrMo alloy. The surface morphology modification and the phase’s transformation induced by the SMAT are evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD).