For buried steel pipelines, cathodic protection should be applied immediately after they are buried in the ground. For pipelines with a long construction period and permanent cathodic protection that cannot be put up in a short time, temporary cathodic protection measures should also be taken for pipelines in a strong corrosive environment. Even for pipelines that have been buried for decades, it is sometimes economically reasonable to apply cathodic protection. To be technically feasible and economically reasonable, the pipeline for cathodic protection must meet the following three conditions:

1, pipe longitudinal continuous conduction

2. Pipe covering layer with sufficient resistance

3. Electrical insulation of pipes and other low resistance grounding devices.

In the case of pipeline corrosion, the surface of the pipeline will have an anode area and a cathode area. In the anode area, the current from the surface of the pipeline steel will flow out into the surrounding electrolyte (soil and water), and the pipeline will corrode in this area. In the cathode region, the current from the electrolyte flows to the pipeline surface, and the corrosion rate in this region will be reduced. The corrosion rate can be reduced by allowing an incoming current to flow at every exposed point on the pipe surface. Precisely, this is what cathodic protection is supposed to accomplish: direct current is forced to flow onto the surface of the pipeline. This direct current can shift the potential of the pipeline in a negative direction, resulting in a reduction in the rate of metal corrosion. When the current is properly adjusted to exceed the corrosion current released from the anode area, a net current will flow into these areas of the pipeline surface, the entire surface of the pipeline will be cathodic protected, and the corrosion rate will be reduced.