Painting a mast?

[neilpride]

Originally Posted by Cherp

I'm pulling the mast this week. Lowest ten feet has bubbling under the paint, which is black. Will sandblast it off. The trick appears to be to get a primer onto the clean aluminium fast, so an oxide layer can't form. From what I've read, it's the formation of this oxide layer on aluminium that causes later paint problems. We'll see how we go.

We are painting a large mast and boom this week from a huge day chárter catamarán , the boom come in a terrible condition, corrosión , paint flaking off , etc etc..

You have a marvelous stuff from Awlgrip for bare aluminium, MaxCor Cf, its a anticorrosive chromate free epoxy primer , very similar used in comercial planes , the stuff stick to bare aluminium really well, its expensive, so far the best stuff for us when we deal with paint corrosión problems ..
Good Luck.

[model 10]

Originally Posted by Cherp

I'm pulling the mast this week. Lowest ten feet has bubbling under the paint, which is black. Will sandblast it off. The trick appears to be to get a primer onto the clean aluminium fast, so an oxide layer can't form. From what I've read, it's the formation of this oxide layer on aluminium that causes later paint problems. We'll see how we go.

You don't really need to worry about that if you treat the surface correctly. You need to acid etch the clean metal then treat it with an alodine. Once you do that, you have plenty of time to apply paint. FWIW, this is how you paint airliners. Lots of Aluminum.

[Cherp]

Awlgrip is not common in Australia. I will look at the acid etch/alodine approach though. Thanks. I would rather not be painting it again in a couple of years.

[model 10]

Originally Posted by Cherp

Awlgrip is not common in Australia. I will look at the acid etch/anodyne approach though. Thanks. I would rather not be painting it again in a couple of years.

You don't need Awlgrip. There are all kinds of LPU that are as good. It's advantage is there are a bunch of additives that go along with it. Often, those additives work in any LPU. The thinners and retarders etc, are all pretty much the compatible with any LPU. When you go to a real paint store, they will most often sell you a generic retarder, thinner with an LPU that can be brushed.

[neilpride]

Originally Posted by Guy

You don't need Awlgrip. There are all kinds of LPU that are as good. It's advantage is there are a bunch of additives that go along with it. Often, those additives work in any LPU. The thinners and retarders etc, are all pretty much the compatible with any LPU. When you go to a real paint store, they will most often sell you a generic retarder, thinner with an LPU that can be brushed.

I dont agree, you cant use anything not related with for example Interlux or awlgrip, or even Nautilux coatings or Alex seal coatings, try to use a ugly hardware store universal LPU thiner in a allready mixed awlgrip batch,
you get what you pay for, Awlgrip its a really expensive stuff , but in the other hand its a really good stuff, my mast its sprayed with Awlgrip since 2002 , today is still showing gloss and so far no corrosión or paint adhesión problems, a LPU couple of coats in top of a alodine alu surface skiping the primer step its a récipe for troubles, in other words , my advice, , dont try to save few bucks in epoxy primer , stick with a one Brand, primer and topcoat, Perfection from interlux is cheaper compared with Awlgrip and easy to work with it, or choose a especific LPU primer and topcoat suited for aluminium substrates avalaible in Australia , forget household and cars products for your boat unless you want the horror few months later,,Cheers...

[Cherp]

What is LPU?

[neilpride]

TWO PART LINEAR ALIPHATIC. POLYURETHANE (LPU).

[model 10]

I still maintain that if they don't sell Awlgrip in your area there are other brands of paint that are just as good. No one is suggesting mixing different brands of activator and paint. The additives that make it, spray better ,roll, tip, brush, flow, dry faster or slower, prevent craters etc. are most often the same thinners whether they are US Paint or brand X. As a matter of fact there are a couple of Awlgrip thinners that make just rolling a finish come out better than tipping and can be used in other brands of LPU.

[sy_gilana]

We repainted ours 8 years ago, still looks great. Used a one part polyurethane a product called V33 for extreme climates.
Its designed for use on TV towers on mountaintops, Lighthouses etc.
Cost was about 50 Euros a Gallon. Bought a paintbrush with a fillable handle, so I could squeeze instead of dipping. Of course pulling it is a better job, but if it only needs paint for cosmetic reasons, why pull it. The paint is a gel when you open the can, do not stir or shake, it is dripless and dries slowly, so it will not crack and craze. It stays soft.

Special paint V33 : wood paint, metal paint, floor paint, aquastop V33

[Cherp]

The current thinking is this - sandblast/acid etch/alodine coat/ Dulux two part expoxy primer by three coats/Dulux two pack gloss by two. What do we think?

[pikv]

Sorry guys
I'm also in Oz. I did my mast 6 years ago. Sanded rough painted with proper etch primer and finished with marine enamel. Heretic I guess. Last year the racers in the fleet decided to do the same when they asked me oh I got it to looking so good. Still as good as new.



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[GILow]

Has anyone tried going from a painted mast back to bare aluminium?

Too much work to get all traces off the mast?

Matt

[Cherp]

Originally Posted by GILow

Has anyone tried going from a painted mast back to bare aluminium?

Too much work to get all traces off the mast?

Matt

That would be the best outcome Matt but there would be pitting on the first ten feet of my mast now where the aluminium has blistered under the paint.

[GILow]

Originally Posted by Cherp

That would be the best outcome Matt but there would be pitting on the first ten feet of my mast now where the aluminium has blistered under the paint.

Bugger... I reckon I will have the same problem now that you mention it.

[minaret]

Originally Posted by Cherp

The current thinking is this - sandblast/acid etch/alodine coat/ Dulux two part expoxy primer by three coats/Dulux two pack gloss by two. What do we think?

Perfect. Masts are one of the few places I generally start with a chemical strip, though.