Sacrificial anodes protect the gears, engine, and other metal parts from corrosion. To prevent the iron in the engine being weakened, a sacrificial anode (made of zinc, magnesium, or aluminium) is used, which is ‘eaten up’ by other metals, such as iron and copper. Sacrificial anodes are consumable items which must be checked every year and replaced when only half remains.
Sacrificial anodes involve basic chemistry
When metals with different electrochemical potential come into contact with each other, galvanic cells are formed. The metal within the galvanic cell with the lower potential becomes anodic and corrodes. In other words, the sacrificial anode corrodes or rusts instead of the other metal.
Different sacrificial anodes for different water
Different sacrificial anodes are used depending on the type of water in which the boat usually operates, i.e. fresh water, brackish water, or salt water. Fresh water requires magnesium anodes, in brackish water aluminium anodes are used, while zinc is typically used in salt water.
Frequently asked questions about anodes
What is a sacrificial anode?
A sacrificial anode is a metal that forms a galvanic cell with more noble metals. Corrosion and rust then take the base metal first.
Why are sacrificial anodes used on a boat?
Sacrificial anodes are used to protect metal parts of your boat, such as gears, trim tabs, and axles.
How often should a sacrificial anode be replaced?
Check your anodes every year. When the anode has shrunk to half its size, it’s time to replace it.
