All around the world, pipelines are used to move water, wastewater, oil and gas, and other materials. Chemical storage facilities typically use pipelines to move products from storage tanks into processing facilities, and offshore oil platforms often use underwater pipelines to move oil and gas to facilities on land.
Other types of applications where metal is exposed to water, including on large ships, metal marine structures and on offshore drilling rigs and structures, cathodic protection is required to help to reduce the effects of corrosion on the steel.
The Basics
When metals are exposed to both water and an electrical current, which is typically the interaction with another type of metal, corrosion occurs. In these cases, the water and the soil, just water, or another material such as concrete, acts as an electrolytic material. This allows the dissimilar metals to have a pathway or a conductive substrate to allow electrons to move. The more active metal is the anode, and the less active metal is the cathode, which is the surface where rust develops.
The use of cathodic protection allows this less active metal to be connected to a sacrificial metal. This creates a source of free electrons in the water or the soil, which means the sacrificial metal rusts or corrodes, protecting the steel in the pipe.
Beneficial Products
Different types of materials, including poly wraps and specific types of coatings, can also be used as part of a system of cathodic protection. These types of products are designed to prevent the exposure of the surface of the steel to the water, soil or concrete, thereby helping to extend the life of both the pipe as well as the sacrificial metal.
Depending on the specific type of application and the potential risk of corrosion, one or more of these products may be used simultaneously on any pipe or metal construction.
