Effect of Zr Addition on the Corrosion of Ti in Acidic and Reactive Oxygen Species (ROS)-Containing Environments

The effect of systematic Zr additions on the corrosion behavior of Ti was studied in both acidic and reactive oxygen species (ROS) containing environments, including macrophage cell culture, simulating inflammation associated with metallic implants. Electrochemical measurements on commercially pure (CP) Ti, Zr, and TiZr alloys showed that increasing Zr additions progressively enhanced Ti passivity in both acidic (HCl) and oxidative (H2O2) environments. However, a Ti50Zr alloy was found with increased pitting susceptibility. Corrosion was also evaluated using mass-spectrometry to determine metal ion release following exposure of the alloys to THP-1 macrophage cell cultures, transformed into either their M1 (inflammatory states) or M2a (tissue repair states) phenotypes. The magnitude of ion release was reduced with increasing Zr contents, consistent with electrochemical observations. Nevertheless, optimized Zr content in Ti should balance both passivity and pitting resistance.