Corrosion behaviour and biocompatibility of boron containing titanium alloys in simulated physiological environments

Abstract

The corrosion behaviour of cast and hot isostatically pressed Ti–6Al–4V–B alloys was studied for several compositions in the <0·001–1·09 wt-%B range. Passivity and corrosion resistance were observed in all of the alloys subjected to cyclic potentiodynamic polarisation (CPP) in phosphate buffered saline. The CPP tests were also conducted in 0·9 wt-% sodium chloride (saline) over a wide potential range. The pitting potentials generally decreased with increasing boron content with the notable exception of the 0·01B alloys, which did not pit. The repassivation potentials generally increased with increasing boron content. When osteoclast precursor cells (macrophages) and osteoclast activating cells (fibroblasts) were cultured on Ti–6Al–4V–B alloy discs, higher levels of macrophage receptor activator of nuclear factor κB (RANK) and fibroblast RANK ligand were expressed in comparison with CP Ti, 316L and Ti–6Al–4V. This suggests that boron containing alloys may facilitate differentiation of osteoclasts derived from macrophages that interact with the prosthetic surface. However, it is not yet known whether the upregulation of RANK or RANK ligand is sustainable over longer periods of time.

Keywords:

• Titanium
• Boron
• Corrosion
• Biocompatibility
• Cyclic potentiodynamic polarisation

We gratefully acknowledge the financial support from the LA Section of NACE International, Western States Corrosion Seminar, Western Area of NACE International, the NACE Foundation and Ms. S. Hall. The scanning electron micrographs used in this article were generated at the Center for Electron Microscopy and Microanalysis, University of Southern California (J. Curulli). We would also like to thank U. Ekerman (Cal Poly Pomona), B. Ulgut (Gamry Instruments) and B. Eggers (Bio-Logic). This work was supported, in part, by a Research, Scholarship, and Creative Activity (RSCA) award from the California State Polytechnic University, Pomona, to S. Alas.

Notes

This article is part of a special issue on the durability of biomaterials and biocorrosion.