Cathodic protection is the protection of the metal being protected by external cathodic polarization to reduce or prevent metal corrosion. It can be implemented in two ways.
(1) Impressed current cathodic protection method;
(2) Sacrificial anode protection method.
Impressed current cathodic protection utilizes an applied current to cause the entire surface of the protected metal structure to become a cathode. If the metal device is subjected to impressed current cathodic protection, connect the metal wire to the negative pole of an external power supply and the other auxiliary anode to the positive pole of the power supply. At this time, after passing through the electrolyte solution, the current passing through the auxiliary anode mainly concentrates on the cathode portion of the metal, causing cathodic polarization of the metal, and the current flows back to the power source through the cathode, thereby lowering the total potential of the metal. If the applied protection current is large enough, the original anode on the protected structure is no longer dissolved. At this time, only the cathode reduction reaction occurs on the metal surface, and the addition is complete protection. The selection of anode materials is continuously developed and perfected for different use conditions. The metal oxide coated anode is made of titanium metal as the substrate, and the surface is coated with a platinum-based metal oxide with high catalytic activity. It has good electrical conductivity and small surface output resistance, and is not corroded by the medium itself; And easy to process and other advantages. It can be adapted to different environments, such as seawater, fresh water, soil and other media.
Sacrificial anode protection is to connect a more negative metal to the protected metal as an anode, which forms a large battery with the protected metal in the electrolyte. The current flows from the anode through the electrolyte into the metal device and the metal device is cathodically polarized for protection.
Application: Cathodic protection of underground metal structures
Ship cathodic protection
Cathodic protection of seawater steel structures
Cathodic protection of reinforced concrete in buildings
Soil cathodic protection