A comprehensive review of plasma electrolytic oxidation (PEO) of tantalum (Ta): Mechanisms, properties, and applications

Abstract

Plasma electrolytic oxidation (PEO) significantly enhances the surface properties of tantalum (Ta), making it more suitable for applications that demand high corrosion resistance, wear protection, and biocompatibility. Ta is known for its excellent corrosion resistance due to the formation of a stable oxide layer. The PEO process enhances this property by producing a dense and stable oxide layer, primarily composed of tantalum pentoxide (Ta₂O₅), which provides superior chemical stability in harsh environments. These oxide coatings significantly improve wear resistance by increasing surface hardness and minimizing porosity. The reduced defect density enhances crack resistance and stress distribution, while the smoother coating surface lowers friction during contact. Additionally, ceramic-like coating that protects against mechanical damage, thereby making it ideal for aerospace and industrial applications. In the biomedical field, PEO-coated Ta demonstrates enhanced biocompatibility and promotes bone integration due to its porous structure, which facilitates mechanical interlocking with surrounding tissues. The process can be tailored to incorporate bioactive materials, further improving implant performance. However, challenges remain, particularly in controlling the porosity of the coatings and optimizing PEO parameters to ensure consistent quality. The efficacy of the PEO process is highly dependent on factors such as electrolyte composition, voltage, and current density, all of which influence the morphology, thickness, and phase composition of the oxide layer. By fine-tuning these parameters, it is possible to achieve coatings with tailored properties that meet the specific requirements of various applications. In summary, PEO coatings significantly extend the applicability of Ta by improving its resistance to wear and corrosion while enhancing its biological properties for medical use, though further optimization is necessary to maximize these benefits. In this context, this review paper discusses the advancements and implications of PEO on Ta for various applications.