The Eagle Ford Shale has been very active in terms of oil and gas exploration since 2009-2010. Pipelines have been installed in record time. The metal pipe has a corrosion protection coating on its exterior. Many times this coating gets nicks in it during installation. These nicks can cause rusting pits into the pipe wall over time. It’s possible for a pit to go completely through the wall, and then there’s a leak. Sometimes the integrity of the welds that hold sections of pipe together is not quite right, and it’s possible that the coating over welds is not applied the right way. These problems can cause severe corrosion over time as well.
Chapman Engineering has equipment that scans pipelines, whether above ground, below ground or under water to look for anomalies in the pipe. These anomalies can lead to corrosion, but more on that in a future blog post.
This is a test station installation.
To protect pipelines and other buried metal from corrosion, Chapman Engineering installs corrosion protection systems. These systems are more often referred to as cathodic protection systems. A major part of every cathodic protection system is the anode bed. Chapman Engineering field crews have holes drilled in the ground near the pipelines to be protected. They drop anodes in the holes and attach wires from each anode to a bonding point on each pipeline. Then they bury the anodes. Each anode acts as a sacrificial metal, meaning it will corrode over time. As it corrodes, it provides a protective electrical current to the pipeline metal, thereby minimizing pipeline corrosion. Once installed, the anode bed might protect the valuable oil and gas pipeline company’s assets for up to 20 years.
Oil and gas pipelines are not the only assets that need cathodic protection. Any metal that touches soil or water should have cathodic protection. That can be underground or above metal storage tanks. It might be a natural gas distribution system in a small town, or in an apartment complex. It might be a storage building, or it might be reinforcing steel in concrete.
Corrosion in a pipe.
Corrosion is basically an electrochemical process, meaning there is an exchange of electrons from the metal of the pipe into the environment. Some soils are more corrosive than others, so each anode bed must carefully designed and installed based on soil types and other factors. Cathodic protection systems involve the application of an electric current to offset the flow of electrons otherwise lost in the corrosion process.
This is a rectifier, which makes AC power into DC power.
A piece of equipment called a rectifier can apply this current to the anodes. In remote areas in which electricity is not available Chapman Engineering crews have installed solar panels for electrical power. The anodes give up electrons which flow to the pipe where they provide protection. So each anode slowly has its metal sacrificed to protect the pipe.
There is more to the process than this, but this should give readers a basic idea about cathodic protection and how it is used to protect metal assets.