Sacrificial Anode

Definition - What does Sacrificial Anode mean?

Sacrificial anodes are easily corroded materials deliberately installed in a pipe or tank to be sacrificed to corrosion, leaving the rest of the system relatively corrosion free.

A sacrificial anode is also known as a galvanic anode.

Corrosionpedia explains Sacrificial Anode

The mechanism of the sacrificial anode protection system is very similar to the reaction mechanism of electrochemical cells. In sacrificial anodes the protected metal is placed on the cathode side and then a more reactive metal or alloy (having a larger potential difference than the protected metal) is chosen and connected to the protected metal as an anode. The redox reaction will proceed spontaneously. An oxidation reaction occurs at the anode, which means that the sacrificial metal will be consumed. At the same time, the reduction reaction occurs on the cathodic side, preventing the protected metal from erosion. Thus, corrosion on the protected metal is successfully shifted to the anode, protecting the metal.

Sacrificial anodes are normally supplied with either lead wires or cast-m straps to facilitate their connection to the structure being protected. The lead wires may be attached to the structure by welding or mechanical connections.

The materials used for sacrificial anodes are either relatively pure active metals, such as zinc or magnesium, or are magnesium or aluminum alloys that have been specifically developed for use as sacrificial anodes.

Advantages of using sacrificial anodes:

  • Can be used where there is no power
  • Lower initial cost
  • Less supervision required
  • Comparatively simple installation and additional anodes can easily be added if the initial installation proves to be inadequate

Sacrificial anodes are used to protect:

  • Hulls of ships
  • Water heaters
  • Pipelines
  • Distribution systems
  • Above-ground tanks
  • Underground tanks
  • Refineries

The anodes in sacrificial anode cathodic protection systems must be periodically inspected and replaced when consumed.

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