Glossary

Sacrificial anode

Also Anode, Zinc anode

What is Sacrificial anode?

A deliberately less noble metal that dissolves instead of the components to be protected. It is a wear part and must suit the water: zinc for salt water, aluminium more universal, magnesium for fresh water.

What matters about Sacrificial anode in practice?

It only works with conductive contact to the protected part — painted or mounted with insulation, it is ineffective. Zinc in fresh water passivates and stops working, even though it still looks intact.

If anodes disappear conspicuously fast, more anode mass does not help; finding the cause does: first rule out stray current, then look at the shore connection.

Which anode for which water?

  • Zinc for salt water.
  • Aluminium for salt and brackish water, versatile.
  • Magnesium for fresh water, because zinc hardly works there.

The engine and drive manufacturer often specifies which material to use.

When must the anode be replaced?

At the latest when about half of the material has gone, usually at the annual haul-out. An anode that still looks new after a season may not be working, for example because of missing contact or the wrong material.

How do you recognise stray current?

Anodes that disappear unusually fast and corrosion on propeller or shaft despite a fresh anode are typical signs. Common causes are the shore power connection and fault currents on board. The term galvanic isolation explains how to break the path via the pontoon.

Related terms

All terms from A to Z

Still unclear?

We are happy to explain it for your specific case.

ContactTo the Academy