Painting aluminum spars?

[David Virtue]

I am buying a wood yawl that has aluminum spars and I would like to paint them myself. Anyone had any experience with such a project? Paint to use?

Thanks, David

[Ian McColgin]

In my limited experience, it's a little easier to get the new paint to stick if the old anodizing is mostly gone.

I've had good luck sanding with 180 or 150 till all the loose stuff is gone, cleaning with solvent, and then using a good primer. Really, the primer coat is key.

Remember to masque the inside of your sail track.

G'luck

[ion barnes]

Cant say too much but, Youshould check with a paint rep. What you need is an epoxy paint I think. Prep with a light sanding to remove the scalely stuff and then clean with a etching solution, then the epoxy. Awlgrip is possible.

[shadow99]

I saved this out of the forum a few years ago, it helped tremendously. Hope it does the same for you.

Rick

Painting Aluminum Spars

advadv@mindspring.com on October 25, 2000 at 12:19:27:
In Reply to: Painting Aluminum Spars posted by Kevin Aldrich on October 24, 2000 at 09:03:14:
I ready the previous reply and am familiar with the product and technique suggested. If you are interested in a much more durable application that is admittedly more time consuming may I suggest what my experience has been with the spars of my two Cape Dory 10,s and Cape Dory 14 catboats.
My information comes from what is successful, long term, in painting aluminum aircraft and aluminum outdoor signs where the job has to last.
The problem begins with the fact that as far as paint systems for metal are concerned, most metals- steel, iron are cathodic surfaces and thats what paint is formulated to stick to beat. Aluminum , brass, galvanised steel,and zinc are anodic and paint adherence is poorer.
Painting aluminum succeesfully involves two steps-surface prep , and then the painting. Both are equally important, but successful prep is really pretty easy.
If you are dealing with mill finish aluminum, it's easier, but I doubt that you are. Virtually all spars OEM furnished are anodised clear ,gold or black finish to prevent corrosion. That's the buggerbear- anodising also limits adhesion. I've tried all the short cuts and variations of the steps listed below so forgive me if I sound like the Voice Of Experience here, but if you don't want to see your nice pretty paint chip where the jaws rub the mast or where the mainsheet block strikes the boom, you'vc got to do the system.
J boats, Melges, Pearsons, et al that come with factory painted spars that hold up terrifically well in hard racing use and salt water all start with bare aluminum. You'll have to wet sand all the anodised surface of the aluminum away- a good 3 or 4 thousands of a inch deep.
Go to an auto body paint supplier and get a conversion coat treatment kit. This is going to convert the anodic aluminium surface to a cathodic one for MUCH BETTER paint adhesion. I like the Dupomt brand. You'll get two bottles. All you'll need is a pair of rubber gloves( dishwashing gloves are fine) and a cheap sponge you'll throw away. The first bottle is a mild phosphoric acid etch solution you'll wipe on and rinse off. The other bottle is a zinc chromate solution you wipe on, let stand, and then rinse off. It will leave a greenish yellow stain on the aluminum. Remember aircraft frames - they are all primed with a yellow green color- not because the military likes the shade- it's the color of zinc chromate aluminum primer.
The auto paint store can sell you an aersol can of special gray primer for ALUMINUM surfaces to be used instead of the above conversion coat. I've used it too. It's quicker, cheaper, and second best. I wouldn't use it again myself.
For painting, the big boys spray. Use a two part epoxy primer (Dupont Corlar) and a two part polyurethane (Dupont Imron). Both are expensive and toxic-you need to use a good respirator but you will duplicate factory looks and performance.
More practical is to come as close as you can rolling with a foam roller and tipping off with a foam brush a made to brush, consumer, not professional product. I urge you to first sand off the anodising and do the conversion coat procedure. It is affordable, requires no tools ,and no special skills
Back to the boat store. I too like the Interlus line. They have a two part, two quart, epoxy primer 2100/2101 at $41.00.The single part Brightside Primer at $18 a quart will do, but again you are sacrificing adhesion and durability. The top coat is again, for first choice, a two part polyurethane. Its safe to use if you're not spraying, but I still recommend wearing a respirator. About $60 at the auto paint place. It'll have two charcoal filters. If it's working right, you won't smell ANY vapors. They're that good. Isocyanite activator is poisonous. Thats what killed hundreds of people in India when the Union Carbide plant had a accident venting to outside air. It will arrest your breathing as well as cause nerve or brain damage. It can be handled safely by an informed amateur, just like a power tool or car, but don't fool around. This is not like getting light- headed on lacquer fumes from a spray can and getting a headache. Outside, fresh air, not in a garage or basement with a water heater or furnace pilot light to ignite the fumes. Even if you go the respiratot route, the fumes will still be there even if YOU can't smell them.Safety First.
The problem is getting a good buff color at the boat store. Woolsey makes a Grand Banks beige two part polyurethane but it's not a traditional catboat color. You can get a custom mixed brushable two part urethane from a Sterling paint dealer,probably $85 to 100 bucks with activator. If you're not leaving the spars exposed to the sun but under a boat cover like I do, you can do what I do, go to a Pratt & Lambert " house " paint dealer and get their industrial "Palgard" epoxy coating and gloss activator in shade 1-159, about $35, almost a perfect match for the Interlux one part Brightside Sun Down Buff which is the name that replaced spar buff- guess it sells better now that there are so few wooden masts that the hardcore wooden boat crowd would want varnish anyway. Of ciurse you could top coat with the single part Brightside Sun Down Buff ( The Briteside Buff is on my 15'Joel White wooden MarshCat catboat deck and it looks great- but- you can scuff it with a fingernail and two part polyurethane is actually harder ( but not thicker ) than gelcoat.
Again, the cheaper and easier sacrifices durability.
Buying a two quart epoxy primer and a quart of top coat is going to give you enough product for three sets of spars your size , and if you go the full etch,conversion coat, epoxy primer and custom color two part polyurethane route, you've spent $175 on materials, let alone the respirator. If you're doing three boats at a go like me, i'ts not so bad, but for just one, maybe the boat store paint makes more economic sense. Still, if you do it yourself there's no yard labor charge.
Well, now you now what specifics and products I can tell you from my own experience. If you follow all the label directions, you'll get a great
looking job- you just need to consider how long it will last. The aluminum rudder and Honda outboard
on my 22' sailboat were painted with the full prep and prime procedure on the bare aluminum, and a wet sand only on the blue factory paint of the Honda, top coated with white Dupont Imron polyurethane in October of 1973. They have both been in the sun, and the boat in the lake here at Lake Lanier in Atlanta ever since. They have only been washed occasionally with soap and water with a terry cloth towel,never waxed. The motor has a tolerable few nicks along hard edges from being handled on and off the mount for trips to the shop. Nowhere has the paint lifted or blistered. What little oxidation occurs washes off leaving a good,if not original "wet look" gloss, far more than the occasionally compounded white gelcoat hull. Going on 24 years now, that recommends the effort and expense using of the professional auto paint materials was well worth it, don't you think.
Of course, the clear anodised spars have only seen rainwater and still look great too, only a little hazy. But then they aren't buff
Good Luck.
Buddy Sharpton

[Gerald]

David
I can't add much to what Shadow has posted. However, my mizzen mast is aluminum and I painted over old paint with auto paint, streak stained it and varnished it. It looks a lot like wood and most people could not tell the difference. My guess is, the most important part is the prep. You can see a picture of the painted mast in building and repair " KATY's launch."
Good luck
Gerald

[rbgarr]

David-

Are you selling AURA II?

I had a hand in building her at Seth Persson's yard (where she was launched as SANKATY III, as you know).

Do you have a buyer for her? Where have you been keeping her? I noticed that she wasn't in Riggs Cove last summer.

[Nicholas Carey]

Zinc Chromate primer before anything else. You can even find 2-part chromate epoxies. Zinc chromate does some sort of magick with the aluminum to make stuff stick to it that ordinary metal primers don't

Take the piece down to bare nekkid aluminum.

Then, ASAP, coat it with zinc chromate primer. Don't dwaddle with getting the primer on as aluminum oxides amazingly quickly—that's one of the reason aluminum is corrosion-resistant.

I believe you can find zinc chromate primer in self-etching flavours at auto-body paint suppliers.

Nasty stuff, wear a quality respirator. It's teratogenic and mutagenic: think about whelping kids with three eyes and flippers.

Weird, sickly yellow-green color, too. Whoo.

If it's good enough for a airframes, it'll probably work pretty good on your spar.

You know, for a topcoat, Dupont's Imron (2-part auto paint) would probably rock. Tough as nails (it's got to take road dings), as UV resistant as it gets. Comes in a zillion colors. Think Oldsmobile beige :D

[JFH]

Was PVA (poly-vinyl alcohol) mentioned? I've used it on aluminum as a primer (sprayed on) and it worked perfectly. It'll even make paint stick to a sheet of vapour barrier.

Has anyone tried the faux painted aluminum mast? You paint the wood-grain so it looks like wood and clear-coat the mast.
Saw it on a carbon fiber mast in an ad at the back of WB. :eek: