# Aluminum boat corrosion



## Nutfarmer (Jun 24, 2022)

What is the best way to repair this type of corrosion? Would the best way to just cut it out and weld new aluminum in or clean it up and fill in the holes?  Will have to disassemble the boat because of styrofoam behind the aluminum. Any ideas on dealing with the corrosion?  I have welded aluminum before , but never with this much corrosion.


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## Ulma Doctor (Jun 26, 2022)

i have seen folks epoxy patch plates and feather out the edges to great success.
i would think that silicone RTV and patch plates would also suffice

as far as the repair i saw with epoxy-
the plates were oversize to the holes they were covering by a 3:1 ratio
prep the plates and base metal with vinegar, or other etching substance or rough the base and plate with coarse sandpaper
wipe down with acetone, lacquer thinner, MEK, carburetor cleaner, brake cleaner *or* 1,1,1 Trichloroethylene (if you have some)
mix up the 2 part epoxy and go to town
lightly clamp , wipe off the excess epoxy
feather edges with sander or just sandpaper
paint if desired


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## aliva (Jun 26, 2022)

It's much more work but I would cut out the affected area and weld in a new piece. Check the aluminum thickness around the corroded area it will probably be pretty thin, so the new piece will  have to be larger than the corroded area. Also install a couple of sacrificial anodes to the transom and don't for get  check the outboard, it may already have an anode.


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## matthewsx (Jun 26, 2022)

Transom repair is serious stuff. 

Here's a resource for epoxy repairs.









						Boat Repair Archives
					






					www.epoxyworks.com
				




I also have access to the ABYC standards, this one might be applicable.

ABYC T-1ALUMINUM APPLICATIONS FOR BOATS AND YACHTS

I'd probably go for epoxy in this case rather than welding unless you can determine what alloy the boat is made from.

No matter what just make sure the boat is safe when you're done, maybe even add some flotation. Boating is fun but also deadly if you do it wrong.

John


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## Nutfarmer (Jun 26, 2022)

aliva said:


> It's much more work but I would cut out the affected area and weld in a new piece. Check the aluminum thickness around the corroded area it will probably be pretty thin, so the new piece will  have to be larger than the corroded area. Also install a couple of sacrificial anodes to the transom and don't for get  check the outboard, it may already have an anode.


The anode on the transom was completely unaffected as the one on the engine. It looks like the one on the transom was mounted with silicone so maybe that was why it didn’t work.


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## Nutfarmer (Jun 26, 2022)

I really appreciate the replies and ideas. As much as I wanted to be out in the water, I think the best approach is going to be to disassemble the boat and weld new sections in. Some of the corrosion areas were patched with epoxy that just pealed off. Probably not done properly.


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## mickri (Jun 26, 2022)

Anodes have to be in direct metal to metal contact to work.  Most corrosion in aluminum boats starts on the inside.  Not the outside so an anode probably won't do any good to prevent corrosion.  You have to be pretty anal about keeping the inside spotless.   Aluminum is one the least noble of all metals.  Put any other metal in contact with aluminum and the aluminum will corrode away.  Even the small amount of iron in dirt can cause corrosion.  Fish hooks, bottle caps, coins, lead and the list goes on and on as to what will cause corrosion in aluminum boats.  Especially in salty or brackish water. 

Trying to fix holes in an aluminum boat is difficult at best even under the best of circumstances.  I would contact the manufacturer of the boat to find out what type of aluminum was used.  Then proceed from there.


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## Nutfarmer (Jun 26, 2022)

The worst corrosion was where someone used steel bolts. It’s welded construction so I figure that is the best way to repair. I need to practice on my tig.


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## Ulma Doctor (Jun 26, 2022)

you can mig the repair DC-  use 5356 wire


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## Nutfarmer (Jun 26, 2022)

As in a spool gun?  I only have a suitcase for mig that I use with the portable welder


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## Ulma Doctor (Jun 26, 2022)

Nutfarmer said:


> As in a spool gun?  I only have a suitcase for mig that I use with the portable welder


no sir, you can use a suitcase welder
use a tip the next size up from the wire size you are gonna use to keep the wire from binding
for example use an .035" tip for .030" -5356 wire
the 5356 is softer than the 4043 and will be sufficient for your repairs


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## Flyinfool (Jun 29, 2022)

I have done MIG of aluminum and do not have a spool gun. The manufacturer of my MIG sells a Aluminum conversion kit, consisting of a Teflon liner to replace the steel liner. and a larger dia cone for more gas flow. They recommend DC reverse polarity, more gas flow of 100% argon, and a lot more power than you would use for the same weld in steel. The Teflon liner is because the steel liner will scuff up the soft AL wire causing bird nesting, the Teflon is also a lot more slippery to also help with birdnesting, the one size bigger tip also helps with birdnesting. You can not leave the Teflon liner in there for steel wire as the steel will quickly wear thru your expensive liner. 

If you did not pick it up, yes it will work, Until you get thru the learning curve of setting up the whole wire feed correctly, expect to clear a lot of birds nests of wire. Then there is the learning curve of actually making the weld. It is not hard, just very different from steel. AL does glow with heat so the weld puddle looks very different and it is harder to judge temperature.


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## mickri (Jun 30, 2022)

What make is the boat?  If it is a Gregor, Gregor is still in business in Fresno, CA.  Give them a call and you will get straight answers from them on the type of aluminum used and how they weld their boats.  They might even have a repair service.  Fresno is only a couple hour drive from you.


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