Cathodic Protection Problems for Gas Pipelines South of Isfahan, Iran

Isfahan is one of the largest cities in Iran. In the southern portion of the city, there were some problems with the cathodic protection (CP) of coated gas pipelines buried in soil. The CP levels decreased as the distance from the CP stations increased. Adding new CP stations, repairing anode beds, and applying more CP current produced no significant improvement. During investigations, it was found that the CP designers had not considered factors such as soil resistivity, electrical isolation, and proximity of foreign structures. The design considered only groundbed resistance, and the result was poor distribution of protective current.