ABSTRACT
The results of open-circuit potential and impedance measurements with mechanically polished[MP-],chemically pickled [CP-and anodically covered [AN-] niobium surfaces were found in accord with the implications of the electrochemical theory. MP- electrode yields a surface of open-structure which promotes preferentially the propagation of cathodic and anodic reactions, i.e. the reactivity of surface towards developing a mixed potential. CP-electrode on the other hand, yields apparently surface of much less open-structure due to the formation of an extended surface 61m which can be readily healed up. In contrast from MP- and CP-surfaces, AN-surface [to 5 volt] yields an impervious resistive film which inhibits almost completely the role of the depolarizer, hence the inertness of the surface. The potential acquired by the electrode is far from being characterized as a mixed potential in the sense of the electrochemical theory