Corrosion Study of Additively Manufactured Hip Implant Acetabular Shells: The Influence of Porous Structure and Post-treatment

Abstract

Additively manufactured (AM) implants are rapidly increasing in the medical field, but corrosion resistance remains an essential concern on the newly developed AM implants. In the current study, three kinds of AM shells were evaluated in a three-electrode system under cyclic polarization and electrochemical impedance spectroscopy with bovine calf serum (BCS). The commercial acetabular shell with BIOFOAM® from MicroPort Inc. was the control group. We hypothesized that the AM shells would demonstrate comparative corrosion properties to the control group. After the corrosion testing, all groups were examined with scanning electron microscopy (SEM) with elemental analysis of energy-dispersive spectroscopy (EDS). Based on results of corrosion experiments, AM shells presented less corrosion current in cyclic polarization, which is supported by electrochemical impedance spectroscopy (EIS). After fitted with the equivalent circuit with EIS data, AM shells exhibited higher resistance of polarization and lower capacitance, indicating higher corrosion resistance. With examination of SEM with EDS, a patchy layer of titanium with higher carbon and oxygen concentration was apparent on the surface of the control group, which might cause the galvanic effect inducing higher corrosion currents. In conclusion, AM shells demonstrated a better corrosion resistance than the control group, but there were several limitations in the current study. Future research is required to fully assess the corrosion properties of implants.