The Offshore Voyaging Reference Site

Q&A: Should I Apply Antifouling Paint To An Aluminum Boat?

Question: I’m thinking of leaving the bottom of my aluminum boat unpainted since I’m afraid of electrolysis caused, or at least made worse, by antifouling paint, particularly if the bottom is scratched. The boat is in fresh water, so she will not foul much.

Answer: There is no reason why properly applied antifouling paint that is intended for aluminum boats should cause or aggravate electrolysis. The key to preventing electrolysis is an isolated ground electrical system, good zinc anodes (or magnesium in fresh water) and an isolation transformer to prevent damage from other boats that are improperly wired when plugged into shore power.

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rene blei

My alloy boat has presently an anti-fouling paint applied.
Its slip is on fresh water, Lake Union, Seattle and frequently go out on salt water. Am told whatever grows on in fresh water comes off in salt and visa versa. So what is the point of painting an alloy hull as it doesn´t corrode to begin with. Maybe a stupid question.


Thanks John,
My experience with fresh and salt water combination hasn´t been long enough and my question is more or less based on what I was told by locals. When on saltwater, we are on the move, and little time for barnacles to attach??


Have a follow up question, regarding ultrasonic growth preventer kit I noticed at the latest boatshow. The manufacturer claimed a pay-back within one year in Florida waters.
If it really works, then sailboat owners should have a lot of feedback…………..I hope.
Many thanks.

Joshua Thompson

Check out these two posts on a homemade ultrasonic antifouling device on an aluminum sailboat: