A comparative study on the corrosion resistance of Ti-6Al-4V produced via material extrusion and other additive manufacturing technologies

This study investigated the influence of process-induced surface features, porosity, and microstructure on the corrosion behavior of Ti-6Al-4V alloy produced by different additive manufacturing (AM) technologies, including emerging sinter-based material extrusion (MEX), well-established electron beam melting (EBM) and laser powder bed fusion (LPBF), and wrought reference material. The investigated manufacturing routes produced sensibly different surfaces, porosity, and microstructures. Potentiodynamic and potentiostatic polarization tests in phosphate-buffered saline (PBS) revealed stable passivity and excellent corrosion performance for all AM alloys, both in the as-built and polished conditions. After polishing, modest variations were detected among manufacturing technologies, suggesting a possible deleterious effect of the intrinsic porosity once exposed to the environment. Immersion tests performed in neutral and acidified isotonic solutions highlighted the onset of selective corrosion phenomena between the α and β phases under deoxygenated acidic conditions, consistent with Volta potential measurements. Long-term immersion in acidified isotonic solution confirmed the detrimental influence of porosity on the corrosion behavior of Ti-6Al-4V, especially for the MEX-produced alloy, where the presence of a macro-defect network promoted localized corrosion propagation.