Electrochemical and impedance characterization of passive films on niobium in alkaline and acidic solutions

• Main Authors: Dragica B. Camovska, Martin Lj. Arsov, Toma P. Grcev
• Format: Article
• Language: English
• Published: Society of Chemists and Technologists of Macedonia 2007-12-01
• Series: Macedonian Journal of Chemistry and Chemical Engineering
• Subjects: passive films; niobium; cyclic voltammetry; electrochemical impedance spectroscopy
• Online Access: https://mjcce.org.mk/index.php/MJCCE/article/view/263

In this work electrochemical characterization of the anodic passive films formed on Nb in alkaline (0.1 – 5 M KOH) and acidic solution (H2SO4) was carried out by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Potentiodynamic measurements yielded a classical electrochemical passivation curve for both alkaline (KOH) and acidic (H2SO4) solution. In addition EIS-measurements were performed at several potentials in order to characterize the Nb/solution, and/or Nb/Nb2O5 / solution interfaces. The impedance behaviour of the passive films on Nb can be adequately described with a simple EEC; Rel in series with a parallel circuit CPE (Q) – Rct(ox). The calculate values of the passive oxide (Nb2O5) films resistivity ranged between 1011–1010 Ω cm with relative dielectric constant ( εf ≈ 14) for KOH-solutions and approx. 2⋅1012 Ω cm for 1 M H2SO4, indicating that the Nb-passive films, generated in acidic solutions, are better corrosion protectors then those formed in alkaline solutions.