Additively manufactured Ti-29Nb-21Zr shows improved oxide polarization resistance versus Ti-6Al-4V in inflammatory simulating solution.

Abstract

Retrieval studies in the past two decades show severe corrosion of titanium and its alloys in orthopedic implants. This damage is promoted by mechanically assisted crevice corrosion (MACC), particularly within modular titanium-titanium junctions. During MACC, titanium interfaces may be subject to negative potentials and reactive oxygen species (ROS), generated from cathodic activation and/or inflammation. Additive manufacturing (AM) may be able to produce new, corrosion-resistant titanium alloys and admixtures that are less susceptible to these adverse electrochemical events. In this study, we characterize the impedance and corrosion properties of three new AM titanium materials, including Ti-6Al-4V with added 1% nano-yttria stabilized ZrO2 , admixed Ti-29Nb-21Zr, and pre-alloyed Ti-29Nb-21Zr. We aim to elucidate how these materials perform when subjected to high ROS solutions. We include conventionally and additively manufactured Ti-6Al-4V in our study as comparison groups. A 0.1 M H2 O2 phosphate-buffered saline (PBS) solution, simulating inflammatory conditions, significantly increased biomaterial OCP (-0.14 V vs. Ag/AgCl) compared to PBS only (-0.38 V, p = .000). During anodic polarization, Ti-6Al-4V passive current density more than doubled from 1.28 × 10-7 to 3.81 × 10-7 A/cm2 when exposed to 0.1 M H2 O2 . In contrast, Ti-29Nb-21Zr passive current density remained relatively unchanged, slightly increasing from 7.49 × 10-8 in PBS to 9.31 × 10-8 in 0.1 M H2 O2 . Ti-29Nb-21Zr oxide polarization resistance (Rp ) was not affected by 0.1 M H2 O2 , maintaining a high value (1.09 × 106 vs. 1.89 × 106 Ω cm2 ), while Ti-6Al-4V in 0.1 M H2 O2 solution had significantly diminished Rp (4.38 × 106 in PBS vs. 7.24 × 104 Ω cm2 in H2 O2 ). These results indicate that Ti-29Nb-21Zr has improved corrosion resistance in ROS containing solutions when compared with Ti-6Al-4V based biomaterials.