Aluminum boat corrosion

[Nutfarmer]

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.

 

[Ulma Doctor]

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

 

[aliva]

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.

 

[matthewsx]

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

 

[Nutfarmer]

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.

 

[Nutfarmer]

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.

 

[mickri]

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.

 

[Nutfarmer]

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.

 

[Ulma Doctor]

you can mig the repair DC- use 5356 wire

 

[Nutfarmer]

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