So the Stealth hulls are near ready for repainting, and I'm now looking at the aluminum beams. They were originally painted with a 2 part epoxy paint, or powder coated. Where they mated with the hulls, and many places where hardware was attached, seawater has gotten under the paint, lifted the paint, and mildly corroded the aluminum. My current plan is to remove the hardware, and sand/bead blast the corroded areas. But before repainting, I'd like to skim coat these areas and fair. I believe that an acid etch is recommended before painting aluminum, should that be done before I bog the bad sections? Other ideas to get a good, long term fix?
Thanks gentlemen!

Dave

Paint doesn't stick to aluminum all that well. I'd send em' off for anodizing. Look for anyone who does mil-spec anodizing. There's a few here in MN that do it.

Anodizing is very expensive, maybe powder coating them?

My concern is filling the pitting in the tubing for cosmetic reasons. Which would be fairly easily with polyester glaze(Doplpin) or epoxy bog(West 410). Could that stuff survive the heat involved with powder coating?

Dave

Gougeon used to sell a 2 part "conversion coating" to treat aluminum before gluing with their epoxies. Part 1 was a phosphoric acid etch; Part 2 was a yellowish chromate solution.

Nasty stuff - I think that's why they no longer have the kit on their web site.

I'm sure someone else has something similar. Google is your friend.

Epoxy and heat dont mix very well, and as you know powder coating is melting the paint onto the metal.

there was corrosion pitting on my 28 year old nacra on mast, boom etc. mainly under stainless fittings. used a dremel and little diamond ball heads, like a dentists, had to go quite deep until the white powder of alloy corrosion stopped coming out, left ugly deep holes

so filled the holes with several thick coats of anti-rust primer

sanded flat and painted over again with silver paint, to match alloy

then cut out some sticky aluminium tape to act as electrolytic barrier and re-riveted the stainless fittings back on with stainless rivets

not a textbook repair but total cost was about $10

3 years later, looks fine

Dave,

people bog and paint aluminium boats all the time. You need to:
1. acid etch/wash
2. apply etch primer (some have highbuild mixed in)
3. bog and sand.
4. paint.

Note that some of the primers have a limited period before top coating is required so read the destructions carefully.

That's great guys! Scarecrow, source(s) for the acid etch/ wash stuff, and the etch primer in the US? Do I really need etching if I bog shortly after sandblasting?
Thanks for the ecouraging responses!

Dave

I don't remember if this is can be used on non-ferrous metals. Better check first.

http://www.ospho.com/

In any case, note the retailers at the bottom of the page. Most hardware stores probably carry it, but I'd think Sherwin Williams would be your best bet.

sources are hard to help with as I'm not in the US go to www.aluminumalloyboats.com

I post there as CTMD

You can go into any auto paint supplier and find a wash/etch for alum. I've used a DuPont product that you wipe on let sit for a bit and rinse with water.

The problem is to get rid of the Aluminum Chloride (stiff white powder) that formed under ss rivets. Then treat to Phosphatize the pits as described. Results are much better than just (temporary) mechanical removal of "some" corrosion.