Correct repair sequence - Saltwater Corrosion

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baracuda

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Hello everyone. Just found this site from posts on THT about repairing aluminum boats.

I bought a 2012 Seaark 170 last year and noticed that I have had water in the bilge. Recently it has been a lot, so i checked all around and filled the hull with water and found no leaks. finally dawned on me to jack the boat off the trailer and BINGO. Right where the boat sits on the bunk there is a crack and a lot of corrosion around. Seems like the crack was from power loading or hitting the trailer too hard. the resulting leak let saltwater into the foam floatation under the seat and stayed there, so basically that area getting attacked from the PT bunks with carpet and waterlogged foam. The hull is .100 welded, so there should be some meat there to work with.

Here's the plan, let me know if i am missing anything or if there is a better way:

1) cut hole in back of seat and remove all foam from the void
2) clean, scrub, buff down the inside
3) flip boat and clean, scrub, buff, acid wash the area
4) have a local guy TIG weld the crack
5) Use metal 2 metal or another aluminum epoxy on the outside to fill all pinholes and build up protection layer
6) paint the repair with barrier coat / primer (or Gulvit??)
7) flip boat and apply barrier coat / primer to area under seat (or Gulvit??)
8) put plastic gutter on bunk boards (post form DaleH)
 

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-Clean corroded area w/ powered mechanical sander/brush head, etc.

-Scrub areas w/ white vinegar and cooper scrub pad and rinse well

-Prime with acid-etching zinc chromate primer

-Fill pin hole corrosion with 2-part epoxy like West System G-Flex 650, a flexible epoxy, or Steel Flex

-Weld crack area or mechanically repair

-Put vinyl gutter material over carpeted bunks

-Perhaps stuff pool noodles into the hole to replace foam lost

In that big 'pitted' area you need to be aggressive and remove all traces of white corrosive, which could make that spot bigger and/or then penetrate the hull. No biggie there, search on 'G-Flex 650' and my name, tons of repair info here on it, including many PFDs from West with pictures. A repair kit of it is only $20-$22.
 
I am not an expert, but that looks pretty thin. I would think about riveting on a long patch.

If you took it to a welder, he would be concerned with how this it is.

I would talk to an aircraft mechanic, the patch would be right down his ally.

When I was in the air wing of the Marine Corp a patch was a fairly common occurrence. Something they taught in Mech School.

Seal the under side of the patch with 3M 5200.
 
thanks for the replies.

There is plenty of meat to weld where the crack is, as the pitted corrosion is just what rests on the bunk. the whole corroded area is probably 3.5" x 8". i have been looking at the G-Flex option as well, would you use something like that to put under a patch to bond instead of 5200?

i have also considered putting a patch like mentioned on the outside with rivets then sealer, then heading inside with gluvit or something similar to back it up.

for the flotation i am going to use OJ and soda bottles with the tops glued on.

trying to get it as close to good as possible. this boat only goes in salt water, but is trailered.
 
baracuda said:
... have been looking at the G-Flex option as well, would you use something like that to put under a patch to bond instead of 5200?
I'll try this again :p , then I'm done ... search on terms 'G-Flex 650' under my name, tons of repair info here on it, including many PDFs from West with pictures, including the repair of large cracks with riveted on patches - look for the cracked canoe repair.

:D

To your question, G-FLex is much thinner and flows better than 5200 ever thought about, since it does not flow at all! Either could work, both MUST be applied to primed material, but if you look at the PDFs and do their application with heat as suggested, you will find that G-Flex will penetrate and permanently seal the tiniest of places that will prevent any water ingestion, whereas 5200 is a goop only slathered on and it 'covers' stuff, but doesn't penetrate or absorb nearly as well. Just my $ 0.02 ...
 
thanks for the advice.

After revisiting the aluminum patch idea, it is too risky in saltwater. If the weld or 5200 were to leak even a drop under the patch and it will eat away undisturbed.

SO. After reading all i could about the G/Flex (thanks Dale), i have ordered a 32oz kit and a yard of 6oz cloth to patch it up. I was worried about the bonding to aluminum but it should not be a problem with a good prep and filling all voids from both sides. Ordered a HF gravity feed blaster gun to try out soda blasting since there will be corrosion cervices all over the inside of the patch area. Have the welder on standby, once I cut out the foam under the seat and see exactly where the crack is originating, will throw a bead on it if its anything on the framing before glassing in.

Hopefully will be able to just raise one side the boat with the engine hoist instead of removing the engine and flipping all the way over.

While i am at it, probably move the 2nd battery into the gun box fwd and add some hatches to the top of the rear bench for more storage. also, moving the trailer bunks out one rib on the boat to keep pressure off the repair area. this is going to be a fun project. will take pics and do a writeup if anyone is interested
 
Have done the patch/solid rivet method, and it works very well, if you fill with proper sealant, like Gflex.

Definitely drill the ends of any cracks.

Blast clean, prime, patch inside & fill outside, prime, paint- done! Will last as long as the boat, as long as you seal correctly.

Hope it goes well for you.
 

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