Sacrificial anode Cathodic protection is a kind of cathodic protection, which is done by using a less valuable material as a sacrificial anode and connecting it to the structure to be protected through a metal conductor. Materials used for cathodic protection of sacrificial anodes are magnesium, aluminum and zinc. They provide electrons to the protected structure to protect it from corrosion, but are themselves consumed by corrosion.
In general, sacrificial anode cathodic protection is used to protect coated areas with low current requirements and low soil or water resistivity. It is also used for protective structures with relatively small surface areas.
A sacrificial anode is a highly active metal used to prevent surface corrosion of less active materials. In sacrificial anode cathodic protection applications, the natural potential difference of different metals is used to provide protection. The sacrificial anode is coupled to the protected structure, and as long as the anode is more "active" than the structure, current flows from the anode to the structure. When the current flows, all the corrosion occurs on the anode, which "sacrifices" itself in order to protect the structure from corrosion.
Chemical composition of aluminum anode
|Types||Zn||In||Cd||Sn||Mg||Si||Ti||Impurities, not more than||Al|
Electrochemical performance of aluminum anode
|Performance, types, indicators||Open circuit potential|
|Actual capacitance A · h/kg||Current efficiency|
|Ordinary aluminum alloy anode||1.10-1.18||1.05-1.12||≥2400||≥85||Corrosion products are easy to fall off and dissolve evenly on the surface.|
|High-efficiency aluminum alloy anode||1.10-1.18||1.05-1.12||≥2600||≥90|
|Highly activated aluminum alloy anode||1.45-1.50||1.40-1.45||≥2080||≥70|