An investigation regarding semiconducting and passive behaviors of coarse- and nano-structured pure Ta in Ringer's physiological electrolyte: role of anodic passive potential

Through this survey, by the application of magnetron sputtering technique, an unprecedented nano-structured (NS) α-Ta was coated on Ti substrate. The provided coating was fully dens, homogeneous in microstructure and with crystals preferable to specific plane of (110). Employing comprehensive electrochemical evaluations, the formed passive layer on the α-Ta coating and pure uncoated Ta in the Ringer's electrolyte at 37 °C were compared in various aspects including the electrochemical response, semiconductivity, donor density (N _D) and the point defects diffusivity (D ₀). The α-Ta coated sample showed much higher corrosion resistance in Ringer's electrolyte than the bare Ta. Moreover, Mott–Schottky analysis revealed a reduced N _D in the passive layer formed on the α-Ta coating compared to that of the pure Ta. The calculated quantities of D ₀ for the α-Ta coating (1.06 × 10⁻¹⁷ cm² s⁻¹) are more than values of the pure Ta (0.94 × 10⁻¹⁷ cm² s⁻¹). The enhanced corrosion resistant behavior of α-Ta coating in the simulated body environment, compared to the pure Ta specimen, can be attributed to the formation of nano-scale microstructure and the crystallographic texture in the coated sample that accelerates the formation of a sturdy and ameliorated passive film with denser structure. (paper)