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Old 08-09-2014, 09:25   #31
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Re: Painting a mast?

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Originally Posted by GILow View Post
Has anyone tried going from a painted mast back to bare aluminium?

Too much work to get all traces off the mast?

Matt
I thankfully haven't had to deal with my spars yet, but I recently grinded off all the Awlgrip paint on my electric headsail furler. It sits at the base of the headstay and the forward most part of the bow, and thus gets hit with a lot of saltwater spray. First the factory paint failed, and then a second application of Awlgrip by a painter who was purportedly a 'pro'. I was all set up to go with the aluminum 2-part etch, Max Cor Cf primer, Awlgrip topcoat system, but then decided to just leave it bare. After removing all the old paint, I polished it shiny. I think when it skins over from oxidation it will look fine. I hope I made the right call since these sealed units are $$$, as is buying a new manual furler of course.

The blistering/paint failures with aluminum always seem to start around the SS fasteners. I use liberal amounts of Tef-Gel whenever possible, and/or nylon washers. On the mast, I scrape off the blistering as much as possible to try and minimize additional oxidation. It's funny, I have had a couple of areas on my powder-coated, aluminum binnacle which have started to bubble. Had some leftover Awlgrip last year and just slapped it on after a light sanding and it's been fine thus far. No doubt a lot depends on how much exposure to saltwater spray.

One area of confusion for me is anodizing. How can one tell the difference between this and bare aluminum? Also, is it like powdercoating where it requires a specialized facility to have it applied? I would think this realistically rules it out for most spars. My vague understanding is that, unlike paint or even powdercoating, the aluminum surface becomes adhered through an electro-chemical process that makes it pretty bombproof. Could be wrong, often am . . . .

Helpful thread, thanks.

Dan
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Old 08-09-2014, 10:19   #32
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Re: Painting a mast?

Anodizing is pretty special process that puts an oxide coating on AL. There are not that many cities that have a shop with a big enough tank to do spars. There is one in Oakland Ca. for example. One of the Spar makers has their masts done there. Most often they add a dye to the bath to give the part some color. If it has no dye you can still tell by looking at the surface. It is very hard and even a drill bit struggles for a tiny bit before it bites.
You can set up your own anodizing tank for small parts but it usually only gets you a thin decorative finish but you can give parts a pretty color with different color dyes. You see this on hose fittings etc.
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Old 08-09-2014, 10:33   #33
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Re: Painting a mast?

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Anodizing is pretty special process that puts an oxide coating on AL. There are not that many cities that have a shop with a big enough tank to do spars. There is one in Oakland Ca. for example. One of the Spar makers has their masts done there. Most often they add a dye to the bath to give the part some color. If it has no dye you can still tell by looking at the surface. It is very hard and even a drill bit struggles for a tiny bit before it bites.
You can set up your own anodizing tank for small parts but it usually only gets you a thin decorative finish but you can give parts a pretty color with different color dyes. You see this on hose fittings etc.
OK, that helps, thanks. Also confirms that I likely have the original Awlgrip on my spars since it doesn't sound like anodizing would bubble, flake, etc. like a paint or powdercoating product. It sounds like the only realistic & lasting solutions on spars & other aluminum components may be carefully prepped LPU or leaving it bare. I hope that's right anyway!
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Old 08-09-2014, 10:48   #34
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Re: Painting a mast?

My surveyor told me never to buy a boat with a painted or powder coated mast.

Then I went and did it. My boat's mast is white powder coated, and the finish, like the boat, is 13 years old. It is bubbling and flaking in a couple of places, but from a distance of more than 2 feet it still looks terrific. I do realize that there is whacking big expense waiting for me some time in the future, however.

Painted masts sure look nicer than bare aluminum ones.

But your money, your choice.
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Old 08-09-2014, 11:04   #35
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Re: Painting a mast?

Noteworthy advice from a surveyor. I heard that the latest round of USCG aluminum pursuit boats all originally came in with painted topsides & decks. Now they are all bare.
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Old 08-09-2014, 11:09   #36
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Re: Painting a mast?

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The spec sheet for strontium chromate primer says it is not suitable for aluminium
This is not true at all. I have been using strontium chromate on my aluminum hull for over twenty years.

Google "strontium chromate aluminum" and you will many brands of marine coatings that use strontium chromate as a primer.

Ultimately, no paint holds to aluminum in a marine environment because of blistering. Aluminum when it does not have its oxide coating will corrode. The aluminum expanding from aluminum to aluminum oxide expands causing the blistering.
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Old 08-09-2014, 11:15   #37
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Re: Painting a mast?

I have considered going bare after stripping all paint. Havent done it on bigger boats because often there are welds, joints and even fillers to smooth them out once stripped! A smaller mast without all that and it might be a great way to go. The other thought I had was to only go bare on the bottom 10 feet or so... or maybe below the first set of spreaders. All the corrosion seems to happen in the lower 6 feet or so... likely from winches, fittings, salt spray etc.
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Old 08-09-2014, 11:24   #38
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Re: Painting a mast?

My only word of caution is to use an aluminum painting system all from one manufacturer. I have painted aluminum parts with Chromate primer from one manufacturer and overcoat from another.. it's stayed gummy it's whole life!
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Old 08-09-2014, 17:44   #39
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Painting a mast?

Go to the auto parts store, buy a few gallons of "aircraft stripper", follow it's directions, a pressure washer is great for removal of the stripper and paint.
Then do as Guy said, Alodine it, first it's great protection from corrosion and it's excellent for promoting paint adhesion.
Google alodine and read about it.

On edit, maybe 1 gl
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Old 08-09-2014, 17:46   #40
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Re: Painting a mast?

Here is alodine, do not skip the alumiprep step though
http://www.aircraftspruce.com/catalo...lodine1201.php
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Old 09-09-2014, 10:57   #41
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Re: Painting a mast?

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Originally Posted by a64pilot View Post
Go to the auto parts store, buy a few gallons of "aircraft stripper", follow it's directions, a pressure washer is great for removal of the stripper and paint.
Then do as Guy said, Alodine it, first it's great protection from corrosion and it's excellent for promoting paint adhesion.
Google alodine and read about it.

On edit, maybe 1 gl
....and probably more importantly, clean out all the fastener holes that attach things to the mast, and get some alodine in the threads etc if you can. Most mast corrosion seems to start with something dissimilar attached.
Then use something on the fasteners when you re install. lanolin, or other products are out there.
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