Where does the current flow during cathodic protection?
For long-distance pipeline, because the pipeline is not equal distance from each point is apart from the anode bed, all point to pipeline cathodic protection current by the resistance of the path is not equal, so the current density is not equal at every point, the anode and the distance protection structure analysis assumes that other factors constant, tank pipe protection structure point of anode current and its distance is inversely proportional to the distance. With the cathodic protection at the bottom of the tank, if the anode is too close to the bottom of the tank, the division of the current is very uneven, causing the side near the anode to over-protect the other side of the protection is not enough. If the distance between the anode and the bottom of the tank increases, the resistance difference of the current loop between each point at the bottom of the tank and the anode decreases, and the current division tends to be uniform. As the distance between the anode and the bottom of the tank increases, the total resistance of the loop increases and the cathodic protection current decreases.
The applied voltage needs to be raised, and the anode will have an optimal position from the perspective of current division. The distance between the anode and the tank bottom should not be less than the diameter of the tank. If there is a mistake, distributed anode or deep well anode should be used. The distance between the upper end of the deep well anode and the ground should not be less than 10m to make the current division uniform. For the long distance pipeline of cathodic protection, the uniform current distribution can be obtained by increasing the distance between the anode and the pipeline or by uniformly arranging the anode. Anode according to the pipeline is too close, will make close to the anode part of the pipeline protection, and far from the pipeline protection is not enough, the anode is too far from the pipeline, will make the whole pipeline under-protection, if the pipeline is fully protected, only to improve the applied voltage. Anode in the best position should make pipe far end get effective protection and aber not happened, because the current is also influenced by soil resistivity, anticorrosive coating condition, pipeline resistance, and many other factors, so the anode and pipe spacing should be not less than 100 m, soil resistivity influence on current distribution uniform when the soil resistivity, pipeline resistance ignoring the timing, The point nearest the anode has the highest current density.