Underground pipelines for any type of system, utility, or process have to be protected from the environment. This environment includes soil moisture, water, and even the soil itself, all which eventually result in corrosion of the pipes.
Pipes can corrode very quickly in the right conditions, mainly where soil moisture and standing water around the pipeline are an issue. Of course, some types of pipe, particularly those made of steel, are very likely to corrode quickly while other alloys, plastic or composite types of pipe are much more resistant to corrosion. The strength of steel or cast iron pipe, however, makes it the best option in many applications.
Protecting the Exterior Surface
There are several options in protection for the external pipe surface. One method that is used around the world and in all different types of environmental conditions is cathodic protection. This is not a new process and has been used since the early parts of the 19th century on ships. It was in the 1930s in the United States where the application was used for underground pipe protection.
As a basic description, cathodic protection turns the pipe itself into one part of an electrochemical cell. It becomes the cathode, and a sacrificial metal becomes the anode, protecting the pipe surface while using the free electrons from the anode.
The key to setting up these systems effectively is to consider all factors that go into the makeup of the given electrochemical cell created. This includes the soil or water and its ability to carry a current as well the surface area of the pipe.
Materials such as a coating and wrappings can be used to enhance the cathodic protection offered for any underground pipes. Coatings and wrap materials can be used on long runs of pipe, fittings or valves, and tape or mastic can be used for complex shapes and around areas that may require additional protection.
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