Corrosion Resistance of Zr 2.5Nb as Material for Permanent Implant

SILVIA B. FARINA; ANDREA GOMEZ SANCHEZ; SILVIA CERÉ

Pisa

Congreso; Eurocorr 2014; 2014

European Federation of Corrosion

Zirconium is a potential material for permanent implants. In particular, surface modification induced by anodisation has proved to be effective to improve corrosion resistance while keeping good osseointegration. The combination of zirconium with niobium is supposed to develop a structure that presents a high corrosion resistance and continues having the mechanical resistance necessary for implants. The aim of the present work is to determine the viability of using anodised Zr-2.5Nb as implant material, and compare it with pure zirconium. The electrochemical in vitro response of anodised samples was studied in order to determine the effect of the surface modification process on the corrosion resistance of these two candidate materials. A simulated body fluid (SBF) solution was selected from literature to investigate the resistance to corrosion. In this study we have assessed the corrosion resistance of the metals using anodic polarisation tests and electrochemical impedance measurements. The presence of Ca-P rich compounds, believed to increase the apatite formation capability in vivo, was also investigated in the as-received and anodised samples after immersion in the SBF solution. Monoclinic zirconium oxide was identified as the main crystallographic phase in the anodised samples of both materials (zirconium and Zr-2.5Nb). Zirconium pyrophosphates, which may be beneficial for further apatite growing in vivo, were also observed. Electrochemical tests performed in the anodizing solution and in the SBF solution revealed that by anodising the materials a higher corrosion resistance is obtained. The improvement on the corrosion resistance is particularly noticeable in the case of the pure metal after a short period immersed in the simulated biological solution. But, after a long period of immersion, the alloy shows better performance. Ca-P compounds were detected only on zirconium anodised at 30 V. Although the presence of these compounds may be beneficial for a good in vivo bone bioactivity of the material, their existence is not mandatory. Thus, as this study have shown the potentiality of using anodised zirconium and Zr-2.5Nb as implant materials from the corrosion point of view, in vivo tests are worth performing in the future to compare the bioactivity of the pure metal with the alloy.