Electrochemical characterization of the passive films formed on niobium surfaces in H2SO4 solutions

Abstract

The electrochemical formation and characteristics of passive films on niobium surfaces in aqueous H2SO4 solutions were studied using open circuit potential and cyclic voltammetry. In the potential region between -1.0 and 1.2 V(NHE), the cyclic voltammetry data showed that the active/passive transition involves slow metal dissolution followed by the formation of semiconducting passive oxide films. The possible electrochemical reactions and the change of the oxidation steps of some niobium oxides occurring in the passive film during the polarization are proposed. A strong influence of the natural air-formed oxide film on the chemical composition of the passive film was shown. This influence makes chemical structure of thin passive films more complicated than that of thick anodic films. It is shown that the passive films consists of more or less stable oxides, such as NbO, NbO2 and Nb2O5. The Raman spectra revealed that the thin passive films were amorphous, while the films formed at higher voltages consist, primarily, of well-crystallized Nb2O5.

Mechanical and electrochemical properties of Nb2O5, Nb2O5:Cu and graphene layers deposited on titanium alloy (Ti6Al4V)

“…5B). This passive layer blocks-out the intrinsic porosity of the coating, leading to decreased corrosion current value [22][23][24].…”

“…In the case of Nb 2 O 5 thin film, decreasing of surface nanohardness after corrosion process, can be due to the passive layer formed on the top of the thin film during corrosion process [22][23][24]. Changes on the surface of uncovered titanium alloy, influenced by the corrosion process, capable of altering the surface hardness, are known and described in [33].…”

Towards Replacing Titanium with Copper in the Bipolar Plates for Proton Exchange Membrane Water Electrolysis

“…The excellent corrosion resistance properties of Nb are due to its ability to passivate spontaneously in contact with oxygen from air or aqueous environments, by forming a thin, highly adherent and stable passive oxide layer on its surface. The thickness of this oxide layer is 2–4 nm and it is extremely difficult to remove from the metal surface [ 32 , 33 ]. The corrosion resistance of Nb can be further increased by electrochemical formation of passive oxide films on its surface.…”

Corrosion Behaviour of High Chromium White Iron Hardfacing Alloys in Acidic and Neutral Solutions

“…11 after potentiodynamic tests in pH 2 and pH 7 buffer solutions showed NbC to be protected from severe corrosion even at FP. The study conducted by Arsova et al [43] also confirmed that stable NbO passive film was detected through Raman spectroscopy in H 2 SO 4 solution.…”