Cathodic Protection Training Course



Module 7

Interference

Interference possibilities.
In order to study interference we must first have understood that we are dealing with electrical energy that simply follows the natural laws that make computers and electronic devices possible.

We can study any interference problem with a computer model



or an actual model in a laboratory.

Proximity of foreign structures and pipelines.
Interference is sometimes called 'stray current corrosion' and happens when two or more electrical circuits are buried or submerged in a common electrolyte.
When a pipeline is coated with a conductive material and passes through an area that has a high electrical potential the whole of that pipeline becomes charged to the level of that area. When it passes into ground of a lower potential the charges leave the pipeline and travel to remote earth to complete their circuit.

This is easily understood when carrying out the 'Three nails experiment' at this link.



This is a simple problem when investigating corrosion leaks on pipelines such as the Nord Stream Pipeline in the Baltic Sea


but more complex when investigating tank bottom leaks in tank farms and refineries.



It must not be forgotten that tank farms and refineries reside on the same ground (electrolyte) as the pipelines that transport the products in and out.