Improving corrosion resistance of additively manufactured nickel-titanium biomedical devices by micro-arc oxidation process

Nickel-titanium (NiTi) alloys have recently attracted considerable attention due to their unique properties, i.e., shape memory effect and superelasticity. In addition, these promising alloys demonstrate unique biocompatibility, represented in their high stability and corrosion resistance in aqueous environments, qualifying them to be used inside the human body. In recent years, additive manufacturing (AM) processes have been envisioned as an enabling method for the efficient production of NiTi components with complex geometries as patient-specific implants. In spite of its great capabilities, AM as a novel fabrication process may reduce the corrosion resistance of NiTi parts leading to the excess release of the harmful Ni ions as the main corrosion byproducts. The main goal of this study is to create and evaluate a micro-arc oxidation (MAO) coating in order to enhance the corrosion resistance of additively manufacture NiTi medical devices. To this end, the process voltage and electrolyte used to produce MAO coating have been investigated and optimized. The corrosion characteristics of the MAO-coated specimens revealed that the proposed coating methodology significantly improves the corrosion resistance of NiTi parts produced using AM process.