<p>This study investigates the influence of different manufacturing routes on the corrosion behaviour of the Ti-25Nb-4Ta-8Sn beta titanium alloy produced by casting, powder metallurgy, and additive manufacturing using selective laser melting. The objective is to elucidate the relationship between microstructure and corrosion resistance in environments relevant to biomedical and dental applications, including simulated body fluids and fluoride-containing solutions. The selectively laser melted samples were intentionally fabricated using processing parameters chosen to promote increased porosity and defect formation to simulate a worst‑case scenario; these features are not inherent to optimised SLM Ti‑25Nb‑4Ta‑8Sn alloys. Consequently, the additively manufactured samples exhibited characteristic microstructural features such as melt pools, partially fused particles, crevices, and interconnected porosity, which influenced their corrosion behaviour. Corrosion performance was evaluated using electrochemical techniques, including open circuit potential measurements, potentiodynamic polarisation, and electrochemical impedance spectroscopy. The selectively laser melted alloy showed higher susceptibility to localised corrosion in neutral environments; however, under aggressive fluoride-containing conditions, it exhibited improved corrosion resistance due to the formation of a more stable and protective passive layer. The corrosion current density in fluoride media was approximately 20 µA/cm² for cast alloy and 2 µA/cm² for printed material. In contrast, the cast and powder metallurgy samples displayed comparable corrosion resistance, with only minor differences under aggressive conditions. The novelty of this work lies in the systematic comparison of corrosion mechanisms across multiple fabrication routes, explicitly accounting for defect-promoting additive manufacturing conditions relevant to realistic biomedical service environments.</p>