Corrosion of 3D-Printed Orthopaedic Implant Materials

3D-printing technologies such as electron beam melting (EBM) have allowed for patient-specific orthopaedic implants, however differences generated from the fabrication process may alter the corrosion properties of Ti6Al4V implants. This study evaluated the corrosion characteristics of EBM-fabricated Ti6Al4V, alongside any linked microstructural and surface changes. EBM-fabricated Ti6Al4V and wrought Ti6Al4V specimens (n = 10 per group) underwent microstructural and surface characterisation before and after corrosion testing. Cyclic potentiodynamic polarisation of specimens was conducted in accordance with ASTM Standard F2129-17. The degree of corrosion damage was subsequently assessed via qualitative and quantitative measures. EBM-fabricated Ti6Al4V demonstrated a higher proportion of β phases and greater surface roughness, compared to wrought Ti6Al4V. Significant differences were observed for all corrosion parameters between the two groups. The lower breakdown potentials (E_b) for EBM-fabricated Ti6Al4V (2.035 V), compared to wrought Ti6Al4V (3.667 V), indicate a lower resistance to pitting corrosion. A greater resultant spread, and severity of corrosion damage was noted on wrought Ti6Al4V. An inferior in vitro corrosion resistance was observed for EBM-fabricated Ti6Al4V. Without post-processing, the rougher surface and differences in microstructure are likely to contribute to this. This suggests potential clinical implications upon in vivo implantation, although corrosion measures remain above recommended minimums.