Influence factors for effectiveness and current status of cathodic protection for buried insulated pipelines

Historical data shows that most of insulated pipelines with cathodic protection suffered from corrosion perforation basically in 2-3 years after they were put into operation. Through field investigation and laboratory simulation, it is confirmed that great limitations exist for the cathodic protection. Based on the basic theory, the factors influencing the effectiveness of cathodic protection are comprehensively analyzed from the aspects of shield of insulation to cathodic protection current, cathodic protection criteria, field measurements of cathodic protection potential and electro-osmotic effect of cathodic protection. It is pointed out that the cathodic protection criteria should be appropriately raised when the insulated pipeline is operating at higher temperature. The routine surface potential values of insulated pipeline are not representative and the metal loss of the pipeline should be detected at regular intervals. In addition to conventional cathodic protection technology, sacrificial anode protection is used and the sacrificial anode is installed in the insulation layer. Then, it can protect the pipes once water ingress in the insulation layer, or solid electrolyte can be used to solve the shielding effect, improving the effectiveness of cathodic protection for buried insulated pipelines.