Iron Keel Epoxy Coating Problems

[01kiwijohn]

Originally Posted by Scaramanga F25

I have had only one iron keel and did the back to iron and quickly cover with coal tar epoxy and then many coats of epoxy to some disappointments 2-3 years later.
I hate to say this but I observed over a few years that other YC members with iron keels were having better luck with several coats of "Rustoleum" painted on. Touch up in the spring.

Good ol' Rustoleum huh? I'm beginning to think that a lot of these high tech, "engineered coatings" are the product of much wishful thinking.
Thanks, I'll certainly look into this.

[01kiwijohn]

Originally Posted by Sail Away 3

Looks like antifouling over Interprotect with rust possible under the Interprotect, Maybe VC 17 bottom paint???
Is antifouling flaking off the Interprotect?
Is the epoxy still attached good to the cast?
How bad is the rust under the epoxy?
Determine what your future plans are.

I am very interested to know as I will be redoing my keel at some point soon.
Ken

It's Micron 66 over Interlux 2000-2001, with ( they think) pettit rustlock primer. (although, that could have been ospho)
As you can see, that bottom paint is adhering to the epoxy but, the epoxy is flaking off the iron keel.
Apart from the chunk, off the forward lower edge, where the hydraulic trailer cross member hit it, there is no rust evident under the primer

[01kiwijohn]

Originally Posted by Benz

Could it be that the keel shrank with the cold, causing the brittle epoxy to crack?

It's possible, I suppose. the lowest temperatures were in the 0 to 10 degree F range, for about a week. (-12 to -17C)

[01kiwijohn]

Originally Posted by s/v Jedi

I would try a specialized primer next time, to go between the keel and the epoxy. I would look into POR-15 and Awlgrip CF Washprimer. Maybe even coaltar-epoxy.

Edit: on my lead keel I used epoxy that I sanded into the lead while the epoxy is still wet (so that no oxygen gets to it).

We did, that's why I paid to have a highly recommended, long experienced boatyard do the job. Previously, I'd haul every 2 years, clean and Ospho any rust patches, then bottom paint it. I'm thinking of going back to that method. Over all, the only difference appears to be that the epoxy requires a lot more specialized screwing around, and about 8 times the cost, averaged over 6 years.

[01kiwijohn]

Originally Posted by Clivevon

Right. Coating Cast iron keels is a real known problem. You need a barrier coat on first before the epoxy. I had this done some years ago. Cant remember the details but seem to recall something about ceramic beads?? If still stuck i could dig back Through my records to see if i can find What they used. 6 years ago & all ok so far...

6 years is where I'm at right now.

[Cheechako]

That doesn't look like a corrosion issue, that looks like incompatible paints or at least a bottom paint coat that didn't bond with the primer. Assuming the light grey is primer.

[darrelweb]

Folks,
Whenever you do any coating of steel or cast iron, especially after sandblasting, grinding or sanding, the bare metal needs to be etched chemically to provide a bonding layer for your primer/epoxy barrier coat.

Some paints have an etch chemical in the paint, but its not the best. Go to an auto paint store and ask for a metal etch for steel/iron. Follow the directions, paint it on, let the chemical provide an oxide layer to the metal, rinse it off, let it dry, then use your Total Boat or Interprotect barrier coat.

I use 4 coats and add another coat when the previous coat leaves a thumbprint. First coat of bottom paint should go on the last coat of barrier coat when it is tacky or when you can leave a thumbprint.

My two cents worth here but steel/iron has to be etched for anything to bond to it.....[emoji847]
Darrel

[bailsout]

I had pretty good success with a rust stabilizer and then splash zone. Always like working with this product. Here’s a crazy thought: try Flex Seal. A dude on the dock put some on his drive below the waterline and said that nothing was growing on it! Good luck.

[kenbo]

Had many iron keels over the years. My hard knocks experience and your keel's experience verifies the problem.

Your problem is not bottom paint incompatibility, it seems well adhered over the hull.

The Rustlok is well adhered to the iron keel, but the epoxy has lost it's bond. Why, your guess is as good as mine but I'm going with differential expansion of the keel and epoxy.

The Rustlok is simply a moisture cured urethane (MCU) paint. Not my favorite but it works and works well on iron keels. Since you started with Rustlok I'd stay with it. hopefully you can get all the epoxy coating off easily if not fair it out by sanding. Repair the current rust spots with a rotary wire brush and treat the bare metal with ospho or similar. don't worry about surface rust the MCU will deal with that. Repaint the entire keel with Rustlok, 2-3 coats. Then lightly sand the Rustlok with 80 grit for obtaining a tooth for the bottom paint, apply your bottom paint, then Bob's your uncle.

Your issue was using epoxy. If you had just used the MCU, POR15 is my go to, you'd be fine. You don't need the epoxy as a water barrier, 3 coats of a good MCU is all the water barrier you need and it's very easy to repair and touch up. You don't need "white metal" to coat with MCU just a clean sound surface. And paint the MCU on a very humid day if you can the cure will be quicker and harder.

[captlloyd]

Originally Posted by 01kiwijohn

Good ol' Rustoleum huh? I'm beginning to think that a lot of these high tech, "engineered coatings" are the product of much wishful thinking.
Thanks, I'll certainly look into this.

Right. We did a conveyor job a few years back that called for a zinc rich primer followed by epoxy. The conveyor was trucked from Ohio to Florida and by the time it reached Florida half the paint had stripped off. George Sutton, renowned steel boat builder, told me not to use this type of primer. He stated the zinc rich primer was weak in strength itself. He recommended Devoe epoxy primer.

[thruska]

Well , when epoxy on any metal is expected to remain adhered, i used a phosphoric acid scub to etch the metal. Rinse with water and when dry, scub in the mixed resin with wire brush as first application. Let that tacky up, then roll on next coat. Repeat as many coats as you require for your intended buildup before bottom coat.. you must suit up for this job appropriately ! You will be tossing your zoot suit in the trash.
ive used on lead and its working fine.
This procedure is the recommendation of the Gudgeon bros from West Systems. Call em up and they will help you.