Bottom paint on aluminum hull

[Gulf Comanche]

Just had this discussion w/ my slip neighbor. My hull, and the rest of the boat, is all aluminum. Why do I need bottom paint? Wouldn't a short haul and pressure wash about every year to 18 months work? Lots cheaper than bottom painting.
Mike
P.S: Good luck to all of you who are staring at the beast Joaquin.

 

[HiDHo]

If you stay in fresh water it would work. Brackish or salt water will cause the barnacles to try to attach themselves. I've heard theories that says if you keep a flow of water moving over your hull they can't start the microscopic attachments, and warm salt water is worse than being up North for the critters. So if you head downstream keep moving or you will attract some un-wanted hull formations.

 

[Gulf Comanche]

I believe you about the barnacles but my slip is in freshwater. All I have on there is green scuz.

 

[boatpoker]

If you ever do decide to anti-foul, be very careful and do your research. Most anti-fouling paints will attack aluminum through galvanic reaction. Aluminum must be epoxy coated before applying anti-fouling paint.

 

[Nomad Willy]

I painted a 16' aluminum skiff w anti-fouling paint .. black.

Much more expensive and time consuming than I thought it would be. Interlux has a good website that gives a rundown of 5coats of this and 2 coats of that. Interlux of course. I was the only one in an Alaskan town of 435 people that had AF paint on the bottom of an aluminum skiff. Three different coatings and 9 coats of paint and much sanding did the deed but it probably was a waste of time and money.
Read the website but I think there was a different approach for different hull materials.

 

[TDunn]

You can use one of the copper free paints with econea as the anti-fouling agent. Do not use a copper based paint.

 

[River Cruiser]

Pluckebaum recommends no bottom paint in fresh water according to a friend with a aluminium boat. Bottom paint if it gets scratched or flakes off leaves a small unprotected area that is more subject damage with everything around it protected. He paints his down the sides & transom 8" with a Interlux product that is safe to use on aluminium to keep the scum off.


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[Panope]

If you ever do decide to anti-foul, be very careful and do your research. Most anti-fouling paints will attack aluminum through galvanic reaction. Aluminum must be epoxy coated before applying anti-fouling paint.

+1

Also, An epoxy barrier coat is an important part of preventing below waterline electrolysis even if no anti-foul is used (It is not clear in post #1 what kind of paint, if any, is on the OP's boat).

Panope has epoxy primer only. No aintifoul. Boat is in salt water for 6 months and on the hard for the other six. I manually clean the bottom 3 times per year (once every 45 days of immersion). When boatspeed slows by .5 knots, I know it is time for a scrub.

Barnacles are 1/4" tall at 45 days.

I use a tidal beach to save hoist costs. It is a vigorous 2 hour work-out followed by a pleasant half day on a beach waiting for the tide.

Steve

 

[Old deckhand]

Painted our Hewescraft, 2 coats of epoxy and two of bottom paint. Boat is dry stored in the winter. This has worked for 5 years and counting.

 

[Panope]

Deckhand, do you remember which anti foul paint is on your Hewes? Someday I may tire of scrubbing and might antifoul. I will probably chicken out and use only aluminum appropriate (no copper) paint.

Back in the day, my dad used TBT (tributyltin floride) and that stuff worked great.

Steve

 

[Xsbank]

I have used Trilux 2, dedicated for aluminum and it sucks. It's good for one year then the creatures clamp on. When I dove on her this summer, in July, 15 months after anti foul, the mussels were hanging, the barnacles were thriving and the oysters were just beginning. They don't grow here in the winter! Except that it's illegal to scrape on the shore up here I would just use a long-handled scraper on the beach. Interlux are thieves, a U.S. gallon of their sh*t paint is over $300 this year and I would rate it about even with Walmart latex. Plus they don't even pass on the savings of not having to bother putting biocides in their paint, our government has decided that having spent the last 50 years decimating fish stocks we should now protect the barnacle. Considering that all American boats still use biocide, many of them love to cruise our waters, that's really going to be a successful program.

Epoxy barrier coats are very expensive to apply on aluminum but will allow you to use copper paint. The only problem with that is if the epoxy is damaged, copper and aluminum Dont like to be together in salt water, the aluminum will dissolve.

I still have about 25 aluminum anodes on my boat...

 

[boatpoker]

There are many other metals in many paints than just copper and none of them like aluminum.

 

[Ghostrider42]

Pluckebaum recommends no bottom paint in fresh water according to a friend with a aluminium boat. Bottom paint if it gets scratched or flakes off leaves a small unprotected area that is more subject damage with everything around it protected.

Pluckebaum is 100% correct.