Help me decide the best way to fix pitting

[DaleH]

Sorry if I am late to the party, but see here ...

https://www.tinboats.net/threads/weeping-water-leak-due-to-corrosion-under-carpeted-bunks.41347/

 

[Zip]

Sorry if I am late to the party, but see here ...

https://www.tinboats.net/threads/weeping-water-leak-due-to-corrosion-under-carpeted-bunks.41347/

Interesting. So the ZC primer will help prevent further corrosion. Do you still have the boat? Hows it holding up? I was planning to avoid it just like @sonny1 did since TotalBoat makes an epoxy primer specifically for aluminum. I like the idea since it does help future pitting from happening.

 

[DaleH]

Still sound ... I sold it, but keep in touch with the new owner.

 

[yeti meat]

Sorry if I am late to the party, but see here ...

https://www.tinboats.net/threads/weeping-water-leak-due-to-corrosion-under-carpeted-bunks.41347/

Thanks very much for your response and link. glad to know the skim coat held up. I need to skim coat with something. Got my aluminum burs in the mail today, so Im gonna do some invasive surgery in the next couple days..
what the die grinder reveals will dictate my next move.

 

[yeti meat]

what not to do to your transom...

 

[kazzer]

Aluminum is always a problem removing oxide, because it instantly corrodes when exposed to air. When anodizing, the material is placed in a bath where the chemical dissolves the oxide and deposits a layer of zinc. As the process continues in the anodizing bath, the zinc is dissolved under water and the process of applying the anodize begins without the presence of air, so no oxide. Unfortunately, on a boat, this is impossible to do on a 'one off' basis. SO! Next best thing, in my opinion, is not to grind the surface, but to wet sand blast it. This will remove all the oxide, and lightly rough up the surface, so the mechanical bond of the surface will enhance the strength of the coating. Grinding is, in my opinion, a bad idea, because it won't get into the pits and removes a lot of metal. Blasters are pretty cheap on Amazon = look for = wet sand blaster kit for pressure washer $30. Amazon.com Use dry play sand with no lumps.
Blow the water off, and apply your coating ASAP. Yes, there will be a slight amount of corrosion, but that will be overcome by the roughness of the sand blast. www.caswellplating.com

 

[Wayne Roberts]

I would wire brush it down good followed by a wipe down with M.E.K. or Acetone and then paint the area (or the whole boat even) with Zinc Chromate. Zinc Chromate stops corrosion dead in it's tracks and prevents any further corrosion. I live in Florida in a high moisture and salt environment and it protects my aluminum boats perfectly.

 

[yeti meat]

Aluminum is always a problem removing oxide, because it instantly corrodes when exposed to air. When anodizing, the material is placed in a bath where the chemical dissolves the oxide and deposits a layer of zinc. As the process continues in the anodizing bath, the zinc is dissolved under water and the process of applying the anodize begins without the presence of air, so no oxide. Unfortunately, on a boat, this is impossible to do on a 'one off' basis. SO! Next best thing, in my opinion, is not to grind the surface, but to wet sand blast it. This will remove all the oxide, and lightly rough up the surface, so the mechanical bond of the surface will enhance the strength of the coating. Grinding is, in my opinion, a bad idea, because it won't get into the pits and removes a lot of metal. Blasters are pretty cheap on Amazon = look for = wet sand blaster kit for pressure washer $30. Amazon.com Use dry play sand with no lumps.
Blow the water off, and apply your coating ASAP. Yes, there will be a slight amount of corrosion, but that will be overcome by the roughness of the sand blast. www.caswellplating.com

thanks for the reply kazzer. I like the cheap sandblasting setup there. I agree with your logic.

 

[yeti meat]

I would wire brush it down good followed by a wipe down with M.E.K. or Acetone and then paint the area (or the whole boat even) with Zinc Chromate. Zinc Chromate stops corrosion dead in it's tracks and prevents any further corrosion. I live in Florida in a high moisture and salt environment and it protects my aluminum boats perfectly.

thanks for the reply Wayne.
I have some zinc chromate here. I briefly tested one of these blisters with my die grinder. looks like the corrosion extends laterally another 1/4" past what is visible..I was surprised it went that far.
Sunday im gonna go to town on this thing hammer and tongs. we will see what is what.
its looking like. I may get my hands on some unobtanium... otherwise known as argon.
if so, I need to do my welding before I do any painting or epoxy work.
ill keep you guys updated.
things go slow here, as amazon prime only takes about 28 days to arrive..

 

[LDUBS]

what not to do to your transom...View attachment 117881

Holy cow! I don't even know what the heck I'm looking at in this pic!

 

[thill]

I have had outstanding success with both gray Marine Tex and JB Weld.

The trick is to wipe down with Acetone or spray with carb cleaner to remove any oil film, and then wire-brush immediately before repair. Then use a hair dryer or heat gun to warm the repair area immediately after application.

Warming it up thins the epoxy a little, and helps give a more secure bond into the "toothed" areas caused by the wire-brushing.

Do a small area at a time, focusing on getting the metal really clean. I've never had either one fail when prepped properly. They are permanent fixes for pitting like you show. Once dry, you can sand, prime and paint as desired.

If the spots are blown all the way through and are really big, there are other things to consider, but these will work for those, too. I might add a metal patch, if bigger than 1/4" hole.

 

[thill]

Disregard my earlier post. I hadn't seen page two. You drilled out a bunch of holes, so an aluminum patch would be in order.

I hope it goes well!

Aluminum burrs are the stuff.

 

[Lost But Happy]

I have had outstanding success with both gray Marine Tex and JB Weld.

The trick is to wipe down with Acetone or spray with carb cleaner to remove any oil film, and then wire-brush immediately before repair. Then use a hair dryer or heat gun to warm the repair area immediately after application.

Warming it up thins the epoxy a little, and helps give a more secure bond into the "toothed" areas caused by the wire-brushing.

Do a small area at a time, focusing on getting the metal really clean. I've never had either one fail when prepped properly. They are permanent fixes for pitting like you show. Once dry, you can sand, prime and paint as desired.

If the spots are blown all the way through and are really big, there are other things to consider, but these will work for those, too. I might add a metal patch, if bigger than 1/4" hole.

Proper Preparation Prevents Piss Poor Performance. Words to live by! lol

 

[yeti meat]

Thanks guys.
Yep aluminum burs cut like butter. Plus you get way more mileage out of them than grinding discs. Do the majority of your work with a bur, then just a little touch up with a disc. Save time and money.

Speaking of which. if you guys want to keep your grinding discs from loading up and becoming useless on aluminum, grab yourself some wax. and hit it with the grinding disc first. Im sure most of you guys already know that, but maybe there's one guy out there it could help.

So, I did some dental work on the larger pitting spots. none of them went all the way through.

So the plan A at this point looks like were welding.....
Plan B involves glue and patching material.

the Mig welder will be here around the new years.
taking the slow boat from china apparently.

Im gonna fill the holes that go all the way through the hull. then ill fill in the dental work I did on the inside.
Finally Ill sand blast it and do a skim coat with G flex on the whole floor to take care of the smaller pitting.

I pretty confident thats gonna work, but I do have my fall back plan just incase.
In my experience having a plan B usually guarantees plan A works. No plan B almost always guarantees plan A will fail. hehehe.

Ther Transom is going to get the glue and riveted patch technique after sandblasting.
The fun part will be making the U channel cap with no brake. I have a plan but we will see...

Thats where we stand at this point. now we wait....

 

[thill]

I just did a transom that was terrible with a MIG. Lot of corrosion through-holes. It worked out great. You can see the pics on this thread:

https://www.tinboats.net/threads/19...build-bouncing-ideas-around.49976/post-501935