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Old 17-10-2020, 16:18   #1
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Over coating epoxy paint

I don't really expect to get any great answers to this question but thought I would ask anyway. What the hell.

Long story I don't care to relate. Bottom line is I have some epoxy paint I want to recoat with a different epoxy. The mfg directions are all for a new paint job; strip to bare metal, blast surface, paint. Alternatively the reps say you can over coat but you need to sand the surface with 80 grit or better. Not a great option for this application.

So if anyone has some good information about an alternate method of preping for overcoat that doesn't involve sanding then I would be happy to hear about it.

Steel boat with existing coatings, just looking to add a new layer of a different coating.

Thanks in advance.
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Old 17-10-2020, 16:50   #2
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Re: Over coating epoxy paint

OK, I think I answered my own question. Ameron prep 88.
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Old 17-10-2020, 18:07   #3
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Re: Over coating epoxy paint

You should be able to overcoat two part with two part. Clean, dry, rough up the base material.
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Old 17-10-2020, 21:27   #4
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Re: Over coating epoxy paint

Yes, rough up. I'd use a 1/2 sheet orbital. If you are careful around welds and radiuses you should be able to us 80 grit on the main surfaces and then use the worn sheets to hand sand the details.

It all depends on what you're really looking to do. Just a tie coat to an overcoat or additional barrier coat protection. You really need a good bond if intending it as additional barrier.
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Old 17-10-2020, 21:34   #5
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Re: Over coating epoxy paint

If you don't sand the old paint, the new epoxy will probably come off in sheets. I've seen it happen. Old paint makes a hard, smooth surface, and with nothing the new paint can grip.
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Old 17-10-2020, 21:56   #6
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Re: Over coating epoxy paint

Hpeer how about whip blasting? Done properly it just lightly abrades the surface.
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Old 18-10-2020, 08:34   #7
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Re: Over coating epoxy paint

Epoxy paint chalks when exposed to UV. If this chalking layer isn't removed via sanding, blasting, etc., then the new paint won't stick. Epoxy exposed to sunlight should always be topcoated to prevent chalking.
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Old 18-10-2020, 10:45   #8
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Re: Over coating epoxy paint

Nobody likes to sand. But unless you are painting with a similar Material over a non fully cured surface - sanding is required to make the stuff stick.
Otherwise it will not adhere properly and minor scrapes will peel it in places.
I recently went to repaint some interior woodwork that someone else painted and just blowing it with air from my compressor knocked it off like a skin.

Sometimes with house paint finishes on interior stuff you can get by with a surface prep liquid like No Prep or a deglosser. But not for really hard finishes like are used on boats.
80 grit is fine for surface prep if you are doing epoxy or fiberglass work or bottom paint. but if this is for your hull in cosmetically visible areas you will have paint that sticks but looks like crap.
Best to give it a quick once over with 80 or 100 grit to knock off the gloss and speed things up but not fully sand it until you use 220 or at least 180 grit before you paint.
The Key yo painting is not putting on the paint it is Surface Preparation.
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Old 18-10-2020, 11:03   #9
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Re: Over coating epoxy paint

I have steel boat too and Yes ya gotta give the base some tooth. Has anyone used Amerson Prep 88 to comment??? Ameron by the way is now PPG.
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Old 18-10-2020, 11:06   #10
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Re: Over coating epoxy paint

It makes no sense to suggest sanding when the poster states he doesn’t want to sand. Obviously he understands that sanding is one option. I am curious to hear about the option he has found.
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Old 18-10-2020, 15:04   #11
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Re: Over coating epoxy paint

Quote:
Originally Posted by captlloyd View Post
It makes no sense to suggest sanding when the poster states he doesn’t want to sand. Obviously he understands that sanding is one option. I am curious to hear about the option he has found.
Thanks,

Here is a link.

http://www.ppghighperformancecoating...2.pdf?ext=.pdf

I am still not sure f its right for me, Its availability, its cost, etc.

I can't seem to find any user comments on it anywhere.
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Old 18-10-2020, 15:28   #12
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Re: Over coating epoxy paint

Wash the surface with mineral spirits before you sand or abrade the surface. This will remove any grease, oil or wax. Do this before you sand otherwise you just grind the contamination into the epoxy.
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Old 18-10-2020, 15:38   #13
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Re: Over coating epoxy paint

Quote:
Originally Posted by hpeer View Post
Thanks,

Here is a link.

http://www.ppghighperformancecoating...2.pdf?ext=.pdf

I am still not sure f its right for me, Its availability, its cost, etc.

I can't seem to find any user comments on it anywhere.

The Prep88 looks like a good cleaner and possibly removes any old epoxy surface film/grease. It doesn't seem like it etches the paint. I did read the instructions, but do you need more to top coat?


My understanding w/cured epoxy paint one needs to sand/etch the surface to get a better bite, otherwise it wouldn't adhere well.
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Old 18-10-2020, 16:03   #14
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Re: Over coating epoxy paint

Quote:
Originally Posted by hpeer View Post
Thanks,

Here is a link.

http://www.ppghighperformancecoating...2.pdf?ext=.pdf

I am still not sure f its right for me, Its availability, its cost, etc.

I can't seem to find any user comments on it anywhere.
You might try calling PPG tech support and see if it will work as a stand alone system. It sure would save a lot of labor.
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Old 18-10-2020, 16:30   #15
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Re: Over coating epoxy paint

I’ve had decidedly mixed results with PPG reps. Not on this topic but same under coatings.

3 reps and 5 opinions kind of thing.

One was an old guy who would keep doing thread drift, could not stay on point.

The other 2 strongly contradicted one another. Not on all points but on critical points.

Still, I will likely give it a try.

Here is ONE of the several inline descriptions.

Quote:
Outstanding Characteristics
Prep 88 is a quick working biodegradable cleaner for removing deposits of oil or grease from metal or previously painted surfaces. When washed off with water, Prep 88 leaves a clean surface with no oily film or residue. Prep 88 cleans better than solvent type cleaners. When dry, the surface is ready for either abrasive blasting (if required) or for application of a protective coating.
Prep 88 reduces repainting costs by avoiding sweepblasting or roughening of old paint systems. Prep 88 is relatively non hazardous to use, as compared with other types of cleaning compounds. Prep 88 contains no caustics, phosphates and no hazardous chlorinated solvents.
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