Cathodic Protection of Pipelines and Temporary Protection

Due to the long construction period of pipelines, it is generally required that magnesium anodes be installed for temporary protection if the soil resistivity is less than 20 Ω·m, and connected to the pipeline through test posts. After the impressed current cathodic protection system is activated, the temporary protection should be removed.

The open circuit potential of magnesium anodes is generally more negative than -1.55V CSE. Since the impressed current potential is generally controlled above -1.55V CSE (positive to -1.55V), the presence of magnesium anodes will not have a negative impact on cathodic protection. On the contrary, if the pipeline is interfered by alternating current, the magnesium anode also serves as a grounding electrode for drainage. However, it is worth noting that although the consumption rate of magnesium anodes will slow down due to the presence of impressed current cathodic protection, they will eventually be consumed over time. At that point, only the steel core will be connected to the pipeline, which may become a leakage point for the pipeline. Therefore, it is generally required that temporary cathodic protection be removed after the impressed current cathodic protection system is activated. The presence of temporary cathodic protection may also cause difficulties in measuring the off-potential of the pipeline in the future.