What Does Cathode Interference Mean?
Cathode interference is a phenomenon that usually occurs underground, in which any metallic material lying near a cathodically protected system tends to become damaged or corroded. This primarily happens with underground pipelines and tanks used by the oil and gas, electrical, and water and sewage industries. The cathode interference is caused by the stray current and the soil receiving a negative potential swing.
Corrosionpedia Explains Cathode Interference
In a normal situation, a large metallic pipeline placed underground is protected with a cathodic protection (CP) system, where a direct current (DC) is injected into the soil near the pipeline that needs to be protected from soil corrosion. Consider this large metallic pipeline as a primary pipeline.
Any other secondary pipeline in the vicinity (e.g., nearby water pipeline, other oil and gas pipeline or power cable) tends to pick up the direct current that is injected to protect the large metallic pipeline. Consequently, the large metallic pipeline suddenly starts receiving the direct current at some other potential because the secondary pipe acts as a secondary groundbed that discharges current and corrodes the point of discharge. Corrosion of the unprotected (secondary) pipeline will occur at all points of current discharge. This process is referred to as cathode interference.