Low conductivity makes titanium poorly suited for long wire lengths and restricts its use to larger diameter, shorter anodes. The use of niobium as a substrate to platinum eliminates many of the problems with titanium. The breakdown voltage of niobium oxide film is approximately 120 volts in most commonly found cathodic protection environments. Although its conductivity is higher than that of titanium, it is often still too low for use in small diameters and long lengths. The principal disadvantage of niobium, however, is its relatively high cost.
Copper is an ideal conductor at virtually any length and diameter suitable for cathodic protection.
The combination of high conductivity and low cost allows copper to be an ideal candidate for use in the design of an anode material. Good conductivity, low cost. The most logical combination of materials would include the use of a platinum outer layer, very thin due to cost, a layer of niobium beneath the platinum to allow for a dimensionally stable anode, and a copper core for both conductivity and economy. The niobium layer should be heavy enough to withstand normal mechanical handling. To properly manufacture an anode material which is composed of multilayers, sophisticated metallurgical processing techniques must be employed to insure integral contact between the metal layers.