Really bad corrosion. How to stop it?

[erictetterton]

Well... after having just about every size tinboat out there, I have finally found a SeaArk superjon. Its an old NC wildlife boat that was auctioned off at a surplus sale. They used it to shuttle fourwheelers across the sound to the outer banks. its seen a lot of use but its still a good boat. SeaArk makes a great boat. It has a bunch of corrosion on the transom that im concerned about. From the water stain lines in the inside of the transom, it looks like they let it sit with the plug in and that may be where the corrosion came from. I want to stop it and do a permanent fix. I have already sanded it down really good. I am thinking about painting the holes with self etching primer and putting fiberglass resin inside the holes, then priming and painting with rustoleum bottom paint from lowes. (Any suggestions to stopping this corrosion would be greatly appreciated).

 

[lckstckn2smknbrls]

Fiberglass won't adhere to aluminum very well and will come loose. Marine Tex would be a better choice.

 

[richg99]

Don't really know, but I would think that 3m5200 for all of the tiny pinhole leaks...and a professional welder for the critical big spots.

 

[Johnny]

Do you have any OSPHO in your shop ???
I know it is for ferrous metals (iron) but I have used it on aluminum
for etching prior to painting and it neutralizes corrosion.

according to their website, there is no mention of aluminum at all, only steel and iron.

but if you have access to a small amount, give it a try on a small space to see how
it may "neutralize" the corrosion.

DON'T DO ANYTHING until you get 100% of the corrosion neutralized and GONE.

This is what I used 10 years ago on an old aluminum sign that was corroded pretty bad.
Similar to OSPHO I suppose. NAPA may carry it.
https://www.por15.com/POR-15-Metal-Prep_p_15.html

 

[huntinfool]

I've had this problem in the past.
My suggestion is to get a sand blaster and use it to clean the corrosion areas. This will even get inside the holes and all the small spots that sanding will not.
There are several epoxies out there for aluminum. One of those will fill all the holes. I did this on my '81 Lowe and it is still running today.

 

[MrSimon]

All you can really do is clean the corroded ares incredibly well (blast, chemicals, sanding, etc etc) and then seal them up (5200, welding, epoxy etc etc).

You can get a LOT more life out of that boat for sure!!

 

[erictetterton]

Yea I'm hoping she isn't beyond repair. I was leaning toward using a product made by 3m called scotch weld dp 460 to fill in the holes and paint over it with rustoleum anti fouling bottom paint. That's about the best solution I can come up with besides taking it to a welder and spending at least a thousand dollars

 

[Natedog57]

I would get some estimates from a couple welding shops before writing off as too expensive. I'd think a good shop could knock it out in a few hours. Once it's done you're not worrying about its structural integrity or fighting small leaks.

 

[PSG-1]

Treat it with Ospho, as mentioned. This will eat up all the 'sugar' on the aluminum, and will etch it for painting.

As for how to fix the holes, truthfully, the best fix is to take a grinder, burr bit and wire wheel, clean those areas up, and have them welded, using ER5356 wire.

Mild porosity that doesn't go all the way through can be fixed by painting with truck bed liner, as you mentioned. In fact, that's exactly how I fixed the hull of my jet boat, and it's still running strong, no leaks.

 

[MrSimon]

I've had really good luck finding off-road or race shops who will do one-off welding jobs pretty cheap. If you do all the prep work, and do it well, they can weld all that stuff up in about an hour .... couple hundred bucks tops.