Conductive Polymer
This anode material has been available since the early 1980’s. The anode material consists of a continuous semiconducting polymer material extruded on a copper wire. The active anode component is carbon contained in a polymer matrix. It is a flexible wire-like anode and is provided on continuous rolls. The material has an outer diameter of 1/2″ with an inner core of #6 AWG stranded copper wire. The anode is also provided prepackaged in carbonaceous backfill. The package is a nylon sheath containing the anode and backfill, provided on continuous rolls. Connections of the inner copper core to a main cable are normally with mechanical crimped connectors. The ends of the anode and connections are normally sealed with manufacturer-provided heat shrink enclosures.
The manufacturers recommended maximum current density for the conductive polymer anode is 16 milliamperes per lineal foot, when installed underground. When this material is used in long-line parallel applications, the attenuation of current in the conductor must be considered. Typically, a heavy gauge parallel copper cable is installed with the anode and multiple connections are made at regular spacings along the anode length. This material is used extensively for long line anode system installed parallel to pipelines in areas where coating has deteriorated or where sub-surface conditions do not permit efficient current distribution from conventional current sources. It is normally installed with a surrounding carbonaceous backfill. Conductive polymer anodes have also been installed in confined areas such as between tank bottoms and non-conductive secondary containment liners.
Conductive polymer anodes can provide uniform low-current density output over their entire lengths. Reports have generally been very good. There are some reports of failures in areas where the wire-like anode was not installed in carbonaceous backfill and accelerated consumption of the carbon occurred. These cases have almost all been related to excessive current discharge in low resistivity wet areas such as creek or stream crossings.
