Heat Exchanger Anode


Why the Heat Exchanger Anode Must be Checked and Changed Regularly

Engine and heat exchanger are made from different metals. These metals must be protected from galvanic corrosion by an anode.  If not, the raw water, flowing through the heat exchanger, acting as an electrolyte, conducts electricity to eat away at the least noble metal (galvanic corrosion is the most common source of heat exchanger failure.


Heat Exchanger Anode. Marine Diesel Basics

Using Anodes to Protect other Metals

Galvanic corrosion of the metals in a heat exchanger can be prevented by using a sacrificial anode - the metal of the anode is consumed instead of the brass or tin in the heat exchanger.

Take care to:

  1. make sure the correct anode is being used for the type of raw water
  2. check the condition of the anode at least every 6 months and the anode is changed when about 50% consumed.

Types of anode:

  • aluminum – can be used in all types of water – salt water, brackish, polluted and fresh water
  • zinc – use in sea water/ salt water. Do not use in fresh water because they are prone to developing a whitish calcareous coating which prevents them from working.
  • magnesium – use in fresh water (electrically very active and will be consumed too quickly if used in salt or brackish or polluted water).


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