Impressed current cathodic protection

        Related parameters

Hull impressed current cathodic protection achieves the purpose of protecting hull steel plates by adjusting protection potential and protection current. Therefore, its most basic and important parameters include protection potential and protection current density.

        (1) Protection potential:

The protective potential, depending on the nature of the metal and the nature of the medium in which it is located, does not vary much. Generally, the best protection potential (hull steel with respect to silver/silver chloride reference electrode) is -0.75~-1.00V, and the operating voltage range of ICCP control-potentiostat is ±2V.

        (2) Protection current density:

The protective current density, in addition to the properties of metals and media, is also affected by the environment and varies greatly. It may include:

·     When the ship is in static seawater and the current density is 150mA/m2, it can quickly reach the protection potential (-0.80V); However, if the current density is less than 40mA/m2, the protective potential can hardly be reached.

·     Whether there is cover on the surface of hull steel plate, the types of cover and the integrity of cover greatly affect the size of the optimal current density. For example, the protective current density required by a fully painted steel plate is much smaller than that required by a bare steel plate: in still seawater, a steel plate coated with three coats of polydiethylene-acetylene coating has a current density of 0.35mA/m2 to instantly reach the protective potential; But the bare steel plate needs 154mA/m2, more than 400 times larger. Another example, the same in static seawater: coated with three polydiethylene acetylene coating steel plate, current density 0.11Ma /m2 as long as a few hours can reach the protection potential; And the bare steel plate, the current density up to 45mA/m2 also takes about 9 days.

·     The sea water is flowing, and the current and wind waves are large and small, and ships are sometimes moored and sometimes sailing, and the speed is fast or slow, all of which affect the optimal protection current density. For example, navigation in bad weather and ice breaking navigation, the need for protection current density is significantly increased. There are many types of hull impressed current cathodic protection devices.