Improving the Corrosion Performance of LPBF- and EBM-Processed Ti-6Al-4V by Chemical Pickling

Ti-6Al-4V is a popular material in the biomedical industry for orthopedic prosthetics production. Moreover, this alloy is well-processable via additive manufacturing (AM) technologies, allowing to tailor the design of the implant according to the specific needs of each individual patient. Nevertheless, AM technologies deploy metal powders, resulting in very rough topologies due to partially melted/adhered residual particles on the surfaces generated. Although this promotes osseointegration, corrosion-induced particle dropping can result in a severe inflammatory response in the patient. To overcome this, a pickling treatment was specifically developed and optimized to decrease the concentration of residual particles, without compromising surface roughness. Specimens produced via laser- and electron beam-powder bed fusion (PBF) were investigated. Three different surface finishing conditions (AM-generated, polished and pickled) were also compared via potentiostatic polarization tests. The specimens that underwent the pickling process proved to achieve lower current densities for long term exposures in simulated body fluid (SBF). Another critical phenomenon that occurs in prosthetics is the release of metal ions over time. To assess this issue, multiple electrochemical tests (potentiostatic polarization, electrochemical impedance spectroscopy) were deployed to assess the effect of the different PBF technologies and heat treatments on the ions release rate of Ti-6Al-4V in SBF.