Pipelines are essential to move everything from oil and gas to water. However, the very nature of pipe, particularly ductile iron pipe, is the risk of corrosion. Corrosion can occur on the interior of the pipe due to exposure to water or corrosive agents, but this can be corrected by using an HDPE sleeve or another type of coating in the interior of the pipe.
Protection for Pipe Exterior
For the exterior of the pipe both polywrap or coatings can be used to provide cathodic protection for pipelines. In the most basic explanation, both of these options in protection provide a barrier that seals off or encases the ductile iron pipe from the soil and any moisture or water in the ground.
Exposure to the soil, particularly with moist soil, creates a very real risk of corrosion. Using polyethylene encasement on the exterior of long or short runs of ductile iron pipe provides an effective cathodic protection for pipelines that is also easy to use. These polywrap materials are graded for specific applications, come in a variety of colors, and are also printed with a warning of corrosion protection use.
The other option is to use specific coatings. These coatings can include tapes, which also require the use of paste to act as a primer, allowing the tape to adhere tightly to the surface of the pipe. With the use of the paste/primer, even irregular surfaces such as valves and flanges can have the necessary protection.
For highly irregular surfaces, cathodic protection for pipelines in the form of mastic is used. This is a dense, putty-like material which is applied at any temperature and then shaped to mold to the surface. Typically, the primer layer is applied, followed by the mastic and then the tape is used on the smooth surface provided by the mastic.