Electrochemical Behavior of Electron Beam Powder Bed Fused Ti536 Alloy under Simulated Inflammatory Conditions

Abstract

Additive manufacturing (AM), as an advanced manufacturing technology, enables the production of personalized orthopedic implant devices with complex geometries that closely resemble bone structures. Titanium and its alloys are extensively employed in biomedical fields like orthopedics and dentistry, thanks to the excellent compatibility with the human body and high corrosion resistance due to the existence of a thin protective oxide layer known as TiO₂ upon exposure to oxygen on the surface. However, in joint inflammation, reactive oxygen species like hydrogen peroxide and radicals can damage the passive film on Ti implants, leading to their deterioration. Although AM technology for metallic implants is still developing, advancements in printing and new alloys are crucial for widespread use. This work aims to investigate the corrosion resistance of in-situ alloyed Ti536 (Ti5Al3V6Cu) alloy produced through electron beam powder bed fusion (EB-PBF) under simulated peri-implant inflammatory conditions. The corrosion resistance was evaluated using electrochemical experiments conducted in the presence of 0.1% H₂O₂ in a physiological saline solution (0.9% NaCl) to replicate the conditions that may occur during post-operative inflammation. The findings demonstrate that the micro-environment surrounding the implant during peri-implant inflammation is highly corrosive and can lead to the degradation of the TiO₂ passive layer. Physiological saline with H₂O₂ significantly increased biomaterial open circuit potential up to 0.36 mV vs. Ag/AgCl compared to physiological saline only. Potentiodynamic polarization (PDP) plots confirm this increase, as well. The PDP and electrochemical impedance spectroscopy (EIS) tests indicated that adding Cu does not impact the corrosion resistance of the Ti536 alloy initially under simulated inflammatory conditions, but prolonged immersion leads to enhanced corrosion resistance for all biomaterials tested, indicating the formation of an oxide layer after the reduction of the solution oxidizing power. These results suggest that modifying custom alloys by adding appropriate elements significantly enhances corrosion resistance, particularly in inflammatory conditions.