Underground Steel Pipe Cathodic Protection Technology

Cathodic protection technology is a kind of electro-chemistry protection technology. Its principle is to add the impressed current on the surface of the metal structures corroded. The structures protected is the cathode, to inhibit the electron transfer which causes the metal corrosion so as to reduce or avoid the occurrence of the corrosion.  

When the metal-electrolyte dissolution corrosion system gets the cathodic polarization, the potential turns negative and the over-potential ηa of the metal anode oxidizing reaction will decrease. Also, the reaction speed will reduce. Hence, the metal corrosive speed will get slower. It is called cathodic protection effect. The protection method that takes advantage of cathodic protection effect to reduce the corrosion of metal equipment is called cathodic protection. The external circuit provides the electron for the metal for the need of the reduction reaction of depolarizing agent so that the metal oxidizing reaction (the betatopic reaction) will be controlled. When the metal oxidizing reaction speed reduces to zero, the metal surface will only take the cathodic reaction of the depolarizing agent. 

The fee for implementing the cathodic protection only occupies 1%~3% of the total cost of the underground pipeline engineering. The service life of the pipeline, however, can be prolonged. Therefore, this technology is approved by more and more people as well as widely promoted for application. 

Diagram of Impressed Current