Principle of impressed current cathodic protection technology

In the natural state of Fe and C in steel, mutual polarization to corrosion potential EC, the corresponding corrosion current is IC, when the cathode polarization is energized, the potential is negative shift, if the potential polarization to E1, the total current is I1, and the corrosion current is reduced from IC to I1, at this time the corrosion is reduced, but not stopped. I1-i1 is the applied cathode current. When the applied current continues to increase and the potential continues to move negatively to the anode equilibrium potential EOFe, the corrosion current drops to zero and completely stops the corrosion, and the applied current increases to I2 (this current is the cathodic protection current). In other words, the potential difference between the original C and Fe is high and the potential difference between them is low, resulting in corrosion velocity of IC size. Cathodic protection passes cathodic current to the metal to polarize the cathode and shift the potential to negative. As a result, the potential difference between cathode C and anode Fe of the original corrosion battery on the metal gradually decreases and the corrosion velocity decreases. When the potential is negatively shifted to equal the potential of Fe (the cathodic protection potential is polarized to about -0.85V, which is relative to the Cu/CuSO4 electrode), the metal is fully protected.