Corrosion resistance and chemical composition investigations of passive layer on the implants surface of Co-Cr-W-Ni alloy

Purpose: The paper presents results of corrosion resistance and surface properties of Co-Cr-W-Ni alloy used in interventional cardiology. Design/methodology/approach: The tests were carried out on grinded, electropolished and passivated samples. The pitting corrosion tests were realized by recording of anodic polarization curves with the use of the potentiodynamic method. The saturated calomel electrode (SCE) of KP-113 type was applied as the reference electrode. The tests were carried out in electrolyte simulating human blood environment (artificial plasma). Crevice corrosion resistance was carried out in accordance to the ASTM F-746-81:1999 standard. Chemical composition investigations of the passive layer were realized with the use of multifunctional electron spectrometer Physical Electronics PHI 5700/660. The X-ray photoelectron spectroscopy with monochromatic radiation AlKα of 1486,6 eV was applied. Findings: Results of electrochemical tests have revealed the influence of surface preparation of the Co-Cr-W-Ni alloy on the corrosion resistance. The tests carried out in the artificial plasma for the grinded, the electropolished and the chemically passivated samples have showed that Co-Cr-W-Ni alloy is resistant to both crevice and pitting corrosion. The chemical composition analysis of the passive layer on Co-Cr-W-Ni alloy has revealed the presence of the following elements: C, O, N, Cr, Fe, Co, Ni and W. Research limitations/implications: The research was carried out on samples, not on final elements. The tests were carried out in in vitro conditions. Practical implications: The suggested surface treatment can be used for implants made of the Co-Cr-W-Ni alloy. Originality/value: The proposed surface treatment ensures the increase of the corrosion resistance in the blood environment that increases biocompatibility.