Zinc, Aluminium or Magnesium Anode
Deciding which sacrificial anode is suitable for your boat depends on the composition of your boat, your drive assembly and the water you are in.
- Ideally the best way is to test your boats potential is with a voltmeter but this is rarely done and in the main, not required.
Firstly the Hull material.
- A fibreglass boat with an inboard engine and bronze and stainless metal parts needs less protection than a boat with an aluminium stern drive.
- Steel, Ferro cement or Aluminium hulls may need more protection again.
- Zinc or Aluminium anodes can't overprotect for this type of hull no matter the volume attached. Magnesium would also work with a fibreglass boat but only in freshwater.
- Aluminium, wooden or steel boats can however be overprotected with magnesium anodes and can cause damage by spooling the paint off.
- Sterndrives and outboards use either zinc or aluminium anodes, with aluminium being more versatile as it can be used in both fresh and sea water.
- Zinc anodes are most suitable for applications in sea water environments, but will form a protective coat in freshwater that renders it useless.
- Magnesium anodes are widely used in freshwater on steel and fibreglass boats.
- If magnesium is used in seawater it will over react and quickly disappear.
- Aluminium works in both environments and is widely used on stern drives and outboards in both sea and fresh water.