Toward scalable TiO ₂ nanotube-coated orthopedic implants: electrolyte reuse, fluoride replenishment strategy, and furnace throughput modeling

Scalable manufacturing of titania nanotube (TiO 2 NT) coatings for orthopedic implants requires robust control of electrochemical anodization and post-anodization thermal processing under production-relevant conditions. While TiO 2 nanotube surfaces have shown promising biological performance at a laboratory scale, industrial translation is constrained by challenges associated with electrolyte reuse, process reproducibility, and annealing throughput. This study addresses these bottlenecks through a combined experimental and process-modeling approach focused on manufacturability rather than biological validation. Three anodization workflows, an optimized ethylene glycol-based ammonium fluoride process, a conventional EG + NH 4 F baseline, and an HF aqueous baseline, were benchmarked on additively manufactured Ti–6Al–4V substrates produced by direct metal laser sintering and electron beam melting. The optimized process produced larger nanotube diameters (108 ± 9.6 nm), higher anatase fraction after short annealing (84.9 ± 1.7%), and improved process yield (90.7 ± 2.3%) relative to baseline methods. Electrolyte reuse experiments revealed predictable fluoride depletion and accumulation of dissolved metallic species with increasing processed area; filtration removed particulates but only a limited fraction of dissolved ions. A simple predictive fluoride depletion model was therefore developed to enable proactive replenishment during reuse. Implant-scale furnace modeling showed that direct energy cost per implant is low, while throughput is governed primarily by cycle time. Overall, the study provides a practical framework for electrolyte lifecycle management and high-throughput thermal processing, supporting industrial-scale production of TiO 2 nanotube-coated orthopedic implants.