What Are The Two Types Of Cathodic Protection?
Aug 24, 2022
There are two types of cathodic protection: sacrificial anode cathodic protection (SACP)and impressed current cathodic protection(ICCP).
1、Sacrificial anode cathodic protection is to connect the metal with more negative potential and the protected metal in the same electrolyte, so that the electrons on the metal are transferred to the protected metal, so that the whole protected metal is at the same negative potential.
This method is simple and easy, does not require external power supply, and rarely produces corrosion interference.
It is widely used to protect small metal structures (current is generally less than 1 ampere) or under low soil resistivity environment (soil resistivity is less than 100 ohm. M). For example, urban pipe network, small storage tanks, etc.
According to the reports of relevant domestic materials, there are many lessons of failure in the use of sacrificial anodes. It is believed that the service life of sacrificial anodes is generally not more than 3 years, and the maximum is 5 years. The main reason for the failure of sacrificial anode cathodic protection is that a layer of non-conductive hard shell is formed on the anode surface, which limits the current output of the anode. The main reason for this problem is that the anode composition does not meet the specification requirements, and the second is that the soil resistivity of the anode is too high. Therefore, when designing the sacrificial anode cathodic protection system, in addition to strictly controlling the anode composition, the anode bed position with low soil resistivity must be selected.
2、Impressed current cathodic protection is to supplement a large number of electrons to the metal through the external DC power supply and auxiliary anode, so that the protected metal is in a state of excess electrons, so that all points on the metal surface reach the same negative potential, and the potential of the protected metal structure is lower than the surrounding environment.
This method is mainly used to protect large-scale or metal structures in high soil resistivity soil, such as long-distance buried pipelines and large tank groups.
Advantages:
High driving voltage, flexible control of cathodic protection current output in a wide range, suitable for occasions with large protection range
It is also applicable in harsh corrosion conditions or high resistivity environment
Long term cathodic protection can be carried out when insoluble or slightly soluble auxiliary anodes are selected
The protection range of each auxiliary anode bed is large, and when the quality of pipeline anti-corrosion coating is good, The protection range of a cathodic protection station can reach tens of kilometers.
complete cathodic protection can also be achieved for the exposed or poor anticorrosive coating
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