Best paint removers to get to bare metal?

[Ninedotsix]

MEK won't cut it.
Methylene Chloride is available, the home depot link is the right gel form, and will work, but you need to keep it from evaporating, so cover with thick (6 mil) plastic, and watch out for eyes, skin and lungs it WILL damage human tissue, as well as being bad for ozone loss. It will take several applications, and is a mess to work with. I hate the stuff.

Heat is very effective, but as stated, the vapors will harm you, so wear an amine/VOC cartridge respirator. You may be able to dodge the vapors by keeping downwind of the smoke.
If the area is in the clear, a "weed burner" supplied with propane fuel will apply enough heat to burn the paint to the metal face.
I'd go that route.
https://www.agrisupply.com/vapor-pro...h-kit/p/32319/

~ 9.6

[raahell]

Well, thanks to everyone for your suggestions.

The problem with all solutions offered is the tight space in which I'm working. only 5" wide, 36" deep and over 7' in length. See pic. It was not designed with repair in mind!

For now I want to get enough of the antifouling and epoxy off to determine if it would be just easier to cut the whole box away and replace with new steel. That would actually be easier than trying to weld cover plates into the existing box. Again it's about the working room.

I've got in there with a small grinder and wire brush to remove some of the stuff and get to metal in areas where the paint has failed. The rest is pretty challenging to remove mechanically. I'm going to try the heating route, for sure, to see how that fairs. I've got a weed killer torch. That may work well in corners where I can't get to mechanically.

In the meantime I did find a Canadian supplier of a stripper gel with both MEK and MC as the active ingredients. The company is called Chembrite (Alberta) and the product is called 222. They also have a non-MEK/MC product called 277 which the rep says is formulated for marine bottom paints. Their minimum size is 20L (5 Ga) so if I go that route I'm going to use it to strip other parts of the hull as well. I've got a respirator for Organic vapours (3M 601) which the company says they use in production but ventilation is still important of course.

I'll let you know how it turns out.

[Ninedotsix]

That picture helps me understand the situation, and I would caution against trying to direct a flame into that space, as it will blow back (and possibly blow out), and that will be very bad for the operator for reasons obvious and not so obvious, like fire in your face, and when the blown out propane reignites.

That said, I'm wondering how much of the surface can be reach from the other side of the box wall. If you can safely play a flame on the box wall enough to heat it to about 180*F, you'll break the bond and be easier scraping. But its better now for me to go back to making a comment on stripping and how it may be preferred method, in the end.

The stripper seems to be formulated for MEK to be the carrier and wetting agent, and the MCL to be the active agent solvent. This mixture should be effective.
Actually, you'll need more than a coat or two to get to completion, so the large package will not be too much.
My experience stripping with MCL on epoxy boat paint is that the stripper doesn't "pop" the paint film like one is accustomed to seeing with enamels or acrylic latex paints, but instead, it soften the surface of the epoxy, and what remains to be done is scouring the scummy surface of the epoxy, and the process took several of these applications, and ultimately sanding. After seeing that the strength of the epoxy film was fully compromised by the chemicals, it seemed necessary to completely remove all remaining epoxy from any area the stripper had been working on.

In fact, one of the aspects of this space that helps the use of the stripper is that it will be relatively easy to close it off after applying the stripper, and that will help keep the active ingredient from flashing off as fast.

But, let me say that the picture does not show a lot of loose scaling epoxy coating or rust. Do my eyes miss that kind of condition?
Would it not be sufficient to seal the existing epoxy paint, and any loose edges where the existing paint may be lifting (not apparent in the picture), and move on to other work?
And, can you help the reader understand the picture from the perspective of how is it that this box is opened up from the top? Did you have to cut it open, and finally, how does it get sealed again?
Sorry to be so inquisitive, but I'm trying to understand the construction practice that leaves the pictured centerboard tackle closed up and seemingly inaccessible, sealed away in a wet well. If you don't mind, what am I missing, here?
Fair Winds
~ 9.6

[Lodbrog1]

Truly, the best product that you can buy unless you have an industrial account is a product called Rock Miracle. It will even soften and remove gel coat. It has been banned largely due to REAL MEK. I was fortunate to have found it online a year ago from some vendor. I ordered 1 gallon for 72 bucks and they sent me a case of 4.....enough for my lifetime. it will burn your skin and perhaps even send you to an early grave if you are not properly protected. And the vapors will even get through your clothes, but it works like no other. As many as 3-6 coats in one application as long as it does not evaporate too fast by convection. The only other option in my scaty eight years of boat work is to wrap an appropriate dimensioned piece of wood, perhaps 5/4 by 3 with the coarsest sand paper you can find and sand away. Happy prepping to you.

[raahell]

Hi Ninedotsix,

Inquisitive is good!

It's hard to take a pic that captures it so I made a quick sketch.

There is a bolted on top plate that has access holes for getting at the tackle. The access holes are covered by bolted on clear panels (not drawn) that allow me to visually inspect without removing the panels.

There are definitely areas of the epoxy have blistered but I don't think the corrosion is that bad based on my tapping with a metal chipping hammer and listening for the differences in tone. But I want to get at least the anti-fouling away fully to make a better assessment. I'm heading down to the boat today and will take a few pics of the areas of concern. I will consider keeping the epoxy that remains intact. The Amercoat Clear Primer allows prior coatings to remain as long as they're well adhered and properly prepped.

The boat is still fully furnished on the inside with the keel box encased in wooden framing so I'm not considering using flame inside the cabin. I'm thinking of heat applications only from inside the box and directed at the corners and around the block attachment tabs where I can't get at mechanically. Warnings have been noted.

I had the same thoughts about the ease of which I could seal the box to prevent the stripping gel from drying out too quickly. with the ambient Temps around 0 Celsius the stripping action will not be quick.

[Ninedotsix]

Nice sketch, and very clear how it all comes together.
I'll watch with interest for your further postings.
Cheers,
9.6