Painting over single part epoxy.

[Rungholt]

Hi guys,
The old owner of my boat was painting with single part epoxy paint above the waterline. I would like to switch to 2 part. However there is no way for me to sandblast the hull. I was planing on grinding the paint down to bare steel and cleaning as best i can, is there anything else i can do to prevent any problems?

 

[bajansailor]

How many coats of single part epoxy are on the hull above the waterline now?
Are there multiple layers, and are they in good condition (ie not peeling off or rusting underneath?)
If they have good adhesion, would it be possible to then apply a two part epoxy on top of the old paint, perhaps by lightly sanding it first to provide a key?

 

[Rungholt]

How many coats of single part epoxy are on the hull above the waterline now?
Are there multiple layers, and are they in good condition (ie not peeling off or rusting underneath?)
If they have good adhesion, would it be possible to then apply a two part epoxy on top of the old paint, perhaps by lightly sanding it first to provide a key?

Iv been told that you cant paint over single part with two part. They will have a bad reaction. Im under the impression that it must be completely removed

 

[bajansailor]

I googled it, and I found that International Paints agrees with your comment above -
Can I put a two-pack product on top of my boat’s single-pack paint? | International https://www.international-yachtpaint.com/au/en/boat-paint-help/expert-advice/can-i-use-a-2-pack-on-top-of-a-1-pack

I wonder if it would be possible to apply a barrier coat over your single part paint?

If you currently have a good paint thickness on the hull, and it is in good condition generally, then maybe your best bet might be to stay with single part paint?

 

[fallguy]

Epoxy is always catalyzed afaik. So, you can purchase a precatalyzed epoxy. In 100% of all cases you need to test the compatibility unless you are already certain they are not.

So, scuff the original paint. Get the solvent for the two part epoxy planned and soak it on a small cloth rag. Then tape the rag to the boat over the test spot. Then a piece of plastic over that and tape it all down so the solvent cannot flash off. Come back the next day and see what has happened to the “one” part epoxy. Remove and fingernail scratch test the original paint.

Is it softer? Is it wrinkled? Or is there no change? No change means compatible.

 

[gonzo]

Any residue of paint left will be an area where the 2 part paint will fail. You need to completely remove it. Chemical removers are one way to go. Otherwise, can you slurry blast?