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Old 01-11-2021, 02:56 PM   #1
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City: San Francisco
Vessel Name: Sarah McLean
Vessel Model: Mainship 30 Pilot
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aluminum window frame paint?

My 2002 Mainship window frames are painted (epoxy) from the factory and starting to fail. Bubbling and chipping. What would be the best (easiest) approach to patching this up..?
I do not want to remove the glass and weatherstripping.
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Old 01-11-2021, 05:09 PM   #2
City: Clearwater, FL
Vessel Name: Seas the Bay
Vessel Model: 1981 42' Hardin Europa
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Can't say that I've done it, but in general, when painting aluminum like that, I've sanded it smooth and cleaned out cavities, primed it with a self-etching spray primer, filled any cavities, sanded to shape and feather the fills, primed the filled areas and around them, sanded to feather as needed, scuffed everything iff needed for the top coat,, and then painted with any good paint compatible with the primer, in my case, normally rattle can. Mask really, really well and use drop cloths, fine overapray goes everywhere.

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Old 01-11-2021, 05:18 PM   #3
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I did essentially what gkesden describes above for my Mainship Pilot 34 aluminum window frames. Using an aluminum etching primer like this one is most critical:

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Old 01-11-2021, 05:25 PM   #4
City: Anacortes
Join Date: Nov 2012
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Shortcuts with aluminum donít always last very long. Any channel under the paint, at edges, hardware or other will cause it to lift in short order.

You can try fixing in place if it is possible to actually prep effectively, but IMHO set your expectations low and donít be surprised if it comes up again measured in months on a window subject to condensation.

One of my dock neighbors painted part of his aluminum house last year with some wizbang product of late. We are both watching and hoping to be wrong and see this one succeed long term.
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Old 01-11-2021, 05:38 PM   #5
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Vessel Model: Willard Nomad 30'
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Interlux has a very excellent guide that covers metal applications. I used it extensively when I put AF on the bottom and Brightside on the topsides. Plenty of detail.

North Western Washington State USA
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Old 01-11-2021, 06:13 PM   #6
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City: Long island
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I just did this job last year. I did remove the frames from the boat.
1- rough sand the frames. It helps the next step
2- paint strip all paint , good and bad
3- power wash frames.
4- repeat step 2-3
5 final sand , prep
6- Variprime frames immediately
7- then sandable prime
8- Awlgrip white
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Old 01-11-2021, 06:15 PM   #7
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City: Pender Harbour, BC
Vessel Name: Gwaii Haanas
Vessel Model: Custom Aluminum 52
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There is no permanent fix. It is the nature of aluminum to form an oxide coating on the outside of the metal. This is the beginning of corrosion of the metal but the coating will protect the metal probably permanently. By coating the al with paint, you are basically keeping O2 away from the surface so a breach that allows damp air or worse to touch it causes corrosion. Because the coating cannot form, there is nothing to stop the corrosion from getting right into the grain of the metal.

See the photo in the first post.

You need to remove the paint back to where it has not failed and you need to get all the corrosion off. All of it. Unfortunately, to get the paint to stick you need to remove the natural coating too, which sets up the process.

Painting aluminum is just wrong. Sorry, but your white windows will never look good permanently. Look at windows that have never been painted, like the ones on my boat. Almost 50 years old and no corrosion. The only corrosion I have had is from 2 layers of al not welded or on a bulkhead that was foamed but lived right next to the stuffing box. No foam, no corrosion even with the salt bath. That's the oxide coating working.

Al is the most corrosion resistant and long lived metal, as long as it's unpainted. Think of what a steel boat would look like unpainted?
Don't believe everything that you think.
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Old 01-12-2021, 10:21 AM   #8
City: Great Lakes
Vessel Model: OA 440
Join Date: Aug 2017
Posts: 655
This is a string from when I repainted the black frames on our boat. The new catalyzed urethane has been on the boat for two years with no issues (Great Lakes).

A few photos from the process... (click on them to enlarge)

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Old 01-12-2021, 12:35 PM   #9
City: Clearwater, FL
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Hey Dave,

I think that is exactly the primer I used, too.

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Old 01-13-2021, 09:17 PM   #10
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City: Carrabelle, FL
Vessel Name: Morgan
Vessel Model: '05 Mainship 40T
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Posts: 1,668
I just redid the doors on our Mainship 400, it has the same issues as yours. I've got a little starting on my window frames as well, so I expect to do them in the future.

I agree that Aluminum should be left bare, but unfortunately, Mainship didn't do that after I think 2003, so all you can do is try to keep them up as best you can.

Anyway, here is the thread on my door refinish. I'm happy with it. Let me know if you have questions.

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repair paint alum

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