A study by potential measurements of a niobium electrode in chloride solutions shows that the corrosion potential is a function of Cl− ion concentration and decreases with the increase of Cl− ion concentration. During polarization, the efficiency of oxide formation is decreased due to preferential adsorption of Cl− ions on the oxide surface acting as a depolarizer for the main anodic process. Impedance measurements of the formed oxide film on niobium in various HCl concentrations reveal that in the presence of chloride, the properties of the surface oxide film are greatly influenced. The results create some doubt that the surface oxide film can act as a perfect dielectric.
National Association of Corrosion Engineers
1984
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