What Does Sacrificial Anode Cathodic Protection (SACP) Mean?
Sacrificial anode cathodic protection (SACP) is a type of cathodic protection where a less noble material that acts as a sacrificial anode is connected by metallic conductors to the structure to be protected. The materials used for this purpose are magnesium, aluminum and zinc. They provide electrons to the structure to be protected and are consumed.
Generally SACP is used for protection of well coated areas where protective current requirements and soil or water resistivity are low. It is also used where the surface area of a protected structure is relatively small.
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Corrosionpedia Explains Sacrificial Anode Cathodic Protection (SACP)
Sacrificial anodes are highly active metals that are used to prevent a less active material surface from corroding. In SACP application, the naturally occurring electrochemical potentials of different metals are used to provide protection. Sacrificial anodes are coupled to the structure under protection and conventional current flows from the anode to the structure as long as the anode is more "active" than the structure. As the current flows, all the corrosion occurs on the anode which "sacrifices" itself in order to offer protection from corrosion to the structure.
Features and benefits of SACP:
- No independent source of electric power required
- Limited affects on neighboring structures
- Anode connections are also protected
- Correct material selection ensures no over-protection, thus avoiding metal embrittlement and coating damage
- No possibility of plant damage due to incorrect connections
- Straightforward to install, operate and maintain
There are two types of cathodic protection on the basis of supplying electrons to a structure:
- Sacrificial anode cathodic protection (SACP) - A less noble material acts as a sacrificial anode.
- Impressed current cathodic protection (ICCP) - An external current source and rectifier is used.
The main difference between the two is that ICCP uses an external power source with inert anodes, and SACP uses the naturally occurring electrochemical potential difference between different metallic elements to provide protection.
Both the SACP and ICCP have different advantages over each other. Selection of which method to use depends on the application, efficiency, operational requirements and cost analysis of a specific project.