Influence of Electrolyte Composition and Voltage on the Microstructure and Growth Mechanism of Plasma Electrolytic Oxidation (PEO) Coatings on Tantalum: A Review

Recently, PEO process of tantalum has been developed as a method of producing corrosion-resistant, hard, wear-resistant, and biocompatible as well as having good adhesion coatings. In this review, we present the results of PEO process of tantalum in three main electrolytes. This review tries to measure the effect of electrolyte composition and voltage that were used within PEO procedure on the surface behavior of the produced oxide coatings on Ta. The results of the PEO treatment of Ta in H4SiW12O40 electrolyte revealed that the morphology of oxide coatings really depends on the PEO procedure time. Density of discharge channels declines as their diameter rises. This leads to an increase in the oxide coating roughness within the PEO procedure of tantalum. In electrolytes of β-glycerophosphate disodium and calcium acetate, the results indicated that the employed voltage significantly affected morphologies, the coatings bond strength and the phase components. However, it affected surface chemical species a little. Finally, in 0.5 M Ca (H2PO2)2 electrolytes, the results revealed that using a precise control on the procedure voltage, tuning the obtained coatings thickness is possible in addition to their roughness, adhesion strength and relative values of the electrolyte type inside the modified surfaces of tantalum.