Blistering paint on freeboard of Aluminium hull looking for a remedy/solution.

[kryg]

I have repainted the 15-meter hull of my boat three times in 30 years; there seems no solution to refilling and repaint it once again because of bubbling.

The aluminum hull is fine; it is just that the water seems to get behind the painted faired filler, over time creating the problem of large areas that have bubbled. When removing the failed filler and paint, the hull is ok.

Question: Rather than fill and paint again, I would like to remove the all the freeboard paint and filler back to the Aluminium hull down to the water line, (there is no issue with the hull underwater).

Is it possible to make aluminum plating fair, (as the boat will have a hungry dog look with plate deformation between the hull frames and stingers) This was, is the original reason the hull was faired and filled with epoxy filler micro balloons and painted? No amount of preparation seems to prevent this problem reoccurring?

Has anyone had the same issues and found a remedy or solution to stop the bubbling or removed filler and paint?

Many thanks for reading this post.

SV. Skoiern IV. Kryg

[billknny]

Maybe my expectations are too low, but to me paint that lasts 10 years seems to be doing pretty good...

[groundtackle]

Aluminum is fussy to prep, needs to be scratched, acid etched and painted with primer within 12-24 hours or it will start to oxidize and adhesion will be compromised. I only know this because I've been researching painting the new aluminum dodger we've made for my boat.



my boat.

[kryg]

Your comment is fair enough, but in fact the filler and paint start to lose the adhision battle by starting to bubble within two years of being repainted and filled, progressively it gets worse as the years roll on. To a point,
I can't stand it anymore, and I go once again into the painting fray.

Originally Posted by billknny

Maybe my expectations are too low, but to me paint that lasts 10 years seems to be doing pretty good...

[ironvalleyfab]

strip, acid etch and coat immediately with alodine. it vastly improves the coating adhesion on aluminum while not being a coating in itself.

it is used alot in the aerospace industry and I have only ever purchased from past employers

[kryg]

Thank you. Yes, you can imagine I do know about preparation now. it seems the paint line finishes at the toe rail. I'm guessing this must be the entery point for the fresh water to leach in between the filler and paint over time.

I'm interested in your dodger, as I want to have one build as well. Can you please send me a picture or diagram of it to compare notes.

Thanks, Kryg.

Originally Posted by groundtackle

Aluminum is fussy to prep, needs to be scratched, acid etched and painted with primer within 12-24 hours or it will start to oxidize and adhesion will be compromised. I only know this because I've been researching painting the new aluminum dodger we've made for my boat.



my boat.

[Racer86]

You need two things, alumiprep and iodine. Goggle will tell you what and how.

[gghanger]

Back in the late '70s I built aluminum fishing trawlers and sailboats (also the privilege to work on "Freedom").....marine grade aluminum is 5086...it's totally impervious to the marine environment (don't confuse it with 6061-T6 )...unless it has to be pretty...on the fishing boats we would take a 7" sanding pad and grind off the factory finish so it does not pit....the surface will turn soft dove gray....the top side will stay grey forever....if it's a bildge style boat with lots of microbaloon filler it probably won't look great.....but if you want absolutely zero maintenance��

[Matt Johnson]

We took our painted aluminum hull down to raw aluminum and kept that as the finish. To answer your question, you can weld on studs and pull out dents like a body shop does, but it still would be next to impossible to get a perfect hull like modern aluminum boats.

Matt

[blueazimuth]

Aluminium is notoriously difficult to paint, unless it is prepared exactly as per paint manufacturer's requirements.
The word is requirements, not recommendations....
Another post mentioned aluprep and iodine - he meant aludine, not iodine, and both are used in preperation: both are trademarks of Awlgrip.

It is so critical that even touching a correctly prepared surface with you bare finger, prior to top coat, will guarantee a future bubble.

A couple of other comments - never put any type of tape on an alumimium boat - its an invitation to corrosion. If you want stripes, they must be painted on.
Boot top, too, must be painted on, and taken well below the waterline so that the antifouling goes on top of the boot paint. Any attempt to have boot meet antifoulong without a decent overlap, also invites corrosion.

[groundtackle]

Originally Posted by kryg

Thank you. Yes, you can imagine I do know about preparation now. it seems the paint line finishes at the toe rail. I'm guessing this must be the entery point for the fresh water to leach in between the filler and paint over time.

I'm interested in your dodger, as I want to have one build as well. Can you please send me a picture or diagram of it to compare notes.

Thanks, Kryg.

Posts and pictures of the dodger will be coming soon on the "build a hard dodge" thread. First coat of primer (corspec135 zinc chromate primer) goes on tomorrow afternoon after a final scratch and acid etch in the morning.
Nick

[pcmm]

Wasn't one of the great benefits to aluminum the fact that you DIDN'T need to paint it? coupled with the PITA of you need special antifouling paint ( read more expensive). Personally I would just strip the paint and leave it.

[Jim Cate]

John, did you know Max and Sandy from the boat Volo when they were liveaboards there in Careel? Their bright red alloy hull had the most successful paint I've ever seen on an alloy boat, and they did it themselves. They are due here in Tassie before Christmas, and I can see if Max will divulge his secrets if you are interested.

Jim

[kmacdonald]

Originally Posted by ironvalleyfab

strip, acid etch and coat immediately with alodine. it vastly improves the coating adhesion on aluminum while not being a coating in itself.

it is used alot in the aerospace industry and I have only ever purchased from past employers

Immediately is the key here. Awlgrip has instructions on how to do it. I think the time between prep and primer is a matter of minutes, not hours.

[GordMay]

Greetings and welcome aboard the CF, gghanger.