Aluminum Boat Refinishing

"Boatbuilding with Aluminum: A Complete Guide for the Amateur and Small Shop"
by Stephen F. Pollard

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A. In response to this question I have refinished a couple of pearly monarchs in the past year. I've decided that the best paint to use for this job would be paint used in the auto refinishing systems 1st sanding with 240 grit paper then cleaning with a mild solvent degreaser ensuring surface is dust free 2nd apply 1 - 2 coats of two-pack etch primer leave for about 4-5 hours then lightly rub with a grey Scotchbrite repeat the degreasing process then its ready to put a top-coat on. I have found that two-pack acrylic paint with a plasticizer additive works best; the additive gives a very durable surface and reduces chips and scrapes. I hope this has been helpful.

A. This is the method for painting aluminum above the water line:
If you sand blast the hull use aluminum oxide sand blasting sand. silicon carbide will contaminate the aluminum. Blast with less than 100 psi and spray sand towards the hull on an angle, blasting head on can wrap the hull and cause a wavy hull.
After sand blasting, prep the aluminum with a metal prep you can get this at an automotive paint supply shop. This will cause a blueing affect, or rainbow affect.
After the metal prep you will need to prime with wash primer. wash primer is a zinc dust ⇦ this on eBay or Amazon [affil links] that is mixed with phosphoric acid usually 50/50 mixture.
When spraying the wash primer spray a light enough coat so that you can see thru it (transparent). Usually if sprayed too thick the wash primer will fail to adhere properly.
Topcoat the wash primer with a 2-part epoxy primer or primer sealer. primer will need a scuffing before final top coating. use 180 grit D/a sandpaper on D/a (dual action) sander. in hard to get to places use red Scotchbrite scuff pad.
Primer/ sealer can be painted usually after a flash time of at least 20 minutes and usually no more than a couple of hours. I'd suggest using a true polyurethane enamel. Imron or equivalent. This is a single stage paint, meaning it shines without needing a clearcoat.
A polyurethane enamel shines without needing polishing and withstands the harsh elements.

A. I've read about finishing aluminum boats and you need to wash the boat with soap and water, then let dry. Wipe it down with enamel or lacquer thinner ⇦ this on eBay or Amazon [affil links] Warning! highly flammable! , then wipe dry with paper towels. Once dry, wipe with a tack rag turning several times. Spray a wet coat of Vinyl Wash Primer. Not a heavy coat, but wet, over lapping several inches. After this has dried, spray it within 24 hours with a couple of coats with a epoxy primer. Once this is done, spray as usual with any automotive paint.

A. Hi, Joey. I think the previously mentioned Aircraft Stripper will prove to be the most effective, although it is very noxious, and to be used only with goggles ⇦ this on eBay or Amazon [affil links] , rubber gloves ⇦ this on eBay or Amazon [affil links] , and excellent ventilation.

But if you've "used many types but not much results", please tell us what they were; otherwise your dialog with a reader could go like this:

    "Try this ..."
"We already did, it didn't work"
    "Okay then, try this ..."
"We already did, it didn't work"
    "Alright then, try this ..."
"We already did, it di"
    "I'M GONNA THROW A BRICK AT YOU, JOEY!!"

Thanks.

A. I have been researching blasting media and there is some good options and information at www.kramerindustriesonline.com/blasting-media/plastic-abrasives.htm. There are some plastic media options that work very well on aluminum.

A. A post further up the list asked about Bondo.
DO NOT under ANY circumstances use Bondo ANYWHERE on a boat; EVER !
Wood, aluminum or what-have-you; NO BONDO.
Some people have the idea that boats are cars. They are NOT. Marine materials are made especially for boats and cutting corners at the Auto Shop will come back and EAT you.
Polyester putty, a two part component will fill any gouges after proper prep. Alodine etch (Alodine 1201 ⇦ this on eBay or Amazon [affil links] ), then primer then two part epoxy coating will do your topcoat.

A. Best to remove all old paint/scale etc from an aluminum hull. If you have a compressor (or maybe not, you can buy one cheap) you can get a SODA BLASTER from Harbor Freight for around $100.00.
To repair leaks or scratches or to replace spots which are badly bent use DURA FIX....it is welded with a propane torch and is easy to use for someone who has never welded b4. I have tried it on structural welds and it is as strong as a TIG weld. Its about $30.00 for 25 sticks... it will do a lot of welding.
Hope this helps.
Swamp Thing aka Sam

3M Marine Sealant

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A. When prepping a mudboat, airboat or any other aluminum boat for hull refinishing, I have always relied on using proper technique and a good final product. First, if you feel it is necessary to remove the old coating because it is compromised (chipping, flaking, cracking, etc.) then grind it out with a DA sander. Alternatively, you could rent, borrow, or buy an aggregate blaster to blast the old coating off.

Fill in any gaps in welds or rivets with a marine-grade caulk or putty - NOT BONDO, that's for autos!- and let it cure.

Then apply the type of coating that is designed for the type of boating you do. Need a abrasion resistant coating with great slip of over land, brush, hyacinths, etc.? Then use a specific coating made for airboats. If you need a coating for high performance, use low drag resistance coatings designed for racing. The coating must match the application.

After you decide which coating to use, apply according to manufacturers specs. If you are unsure, call them. They know their product better than anyone on the planet. They will have tips, tricks and product specific advice on the best techniques and conditions to apply.

A. Hi Arnie.

I'm not certain if things are exactly the same in Alaska with your much lower temperatures, but around here it's simple: bare aluminum is fine for fresh water, but will be choked in barnacles in 72 hours if left in salt water.

Regards,

A. Hi Bill.

Aircraft stripper is a non-caustic paint stripper and will remove the paint without damaging the aluminum.

But aircraft stripper contains methylene chloride and can easily damage you: use only outdoors, wearing rubber gloves ⇦ this on eBay or Amazon [affil links] and goggles and following every precaution on the can. And make it a one-time thing -- don't get used to using aircraft stripper.

You can use a zinc phosphate primer ⇦ this on eBay or Amazon [affil links] rather than epoxy. Car paint is no better or worse than other paint; it should be fine. I can't comment on the experience of your friend's friend except to say that if the story is reliable then the paint is reliable. Good luck.

Regards,

A. Hmmmm. I once had an aluminum boat which I painted with ordinary hardware store enamel. It stayed in salt water for 4 or 5 months for several summers.

Never saw a barnacle.

Hi Jeff. I don't doubt your experience, but living on a salt water lagoon for 15 years -- whether the bulkhead was pressure treated wood or fiberglass ... whether the ladders were wood, aluminum, or stainless steel ... whether the outboard motors and outdrive parts were rubber, or steel, or aluminum ... whether it was a row boat or a cruiser or a jet ski: barnacles would start within just a few days, and the only thing that prevented them was ablative copper bottom paint.

Tributyltin

There was a time when organo-tin paint was available, and it would stop barnacles, and I think it was okay to use on aluminum, but it was an environmental disaster and is forbidden everywhere these days.

Regards,

I dunno', Ted. You were in NJ, I was 40 miles North of Boston. I don't recall ever seeing a barnacle on a boat, pier or anywhere. Maybe the water up there is too cold?

Sorry, I'm no marine biologist; I only know what I see here :-)

Regards,