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Old 29-06-2015, 20:43   #1
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methylene chloride to remove interior paint from hull

I've read many posts cautioning not to use paint stripper with methylene chloride "on fiberglass", but it seems like all the caution revolves around potential damage to gelcoat.

I want to remove layers of unknown paint from inside the chain locker. I've done ground away much of the paint that the grinder can reach and now have to use a stripper. I'd like to use one that gets the job done and not waste a lot of time.

I know it's toxic and I have respirators/suits/gloves, but what I'm looking to find out if it will damage the actual fiberglass, which is polyester resin and roven woving. There is no getlcoat. This is inside the chain locker.

Thanks
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Old 29-06-2015, 20:51   #2
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Re: methylene chloride to remove interior paint from hull

In the anchor locker is a drain. If any of the stripper goes through that, it will play hell with the exterior gelcoat. That would ruin your whole day. Stick with heavy grit sandpaper for this odious job.
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Old 29-06-2015, 20:59   #3
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Re: methylene chloride to remove interior paint from hull

Roy,

Thanks for mentioning the drain. I didn't think of that, but in my case, the locker drains to the interior, no exterior drain. I've also dammed up the area so nothing flows into the bilge ( then to the transom where it would hit the gelcoat).

Is it just gelcoat that is an issue or does this chemical damage polyester resin (30 years old)?

Sanding would be an alternative, but there are some area that I just can't reach.
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Old 29-06-2015, 22:05   #4
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Re: methylene chloride to remove interior paint from hull

Go for it. I've ruined the surface of some fiberglass parts with that kind of stripper before but a heavy coat of primer fills in the damage in just fine. I think it attacks the resin but not that bad. If you did it on the outside, you would have a lot of labor getting it smooth again but with what you are doing I wouldn't think twice, execpt for the mess, which would keep me from using it.
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Old 30-06-2015, 00:23   #5
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Re: methylene chloride to remove interior paint from hull

FYI, gelcoat IS (pigmented) Polyester Resin. So, given that, if the stripper damages gelcoat... Then it stands to reason that it wont be the friendliest substance to use on non-colored resin.
And also, the type of stripper which you're referring to, is severe enough to damage epoxies, at the molecular level (structurally). So, were it me, I'd stay away from that type of stripper.

There are, however, other types of strippers, which wont be nearly so harsh; on the boat, or the user. Citrus based ones for example.
It just takes a little digging, & question asking in order to find out what product will suit the task best, sans collateral damage. Or requiring a hazmat suit.

If you want the full story on the stripper that you're thinking about using:
- Get on the phone with them until they give you some Solid answers, regarding it's effects on Polyester Resins.
- Dig around on the manufacturer's website, & those of other companies which make comparable strippers, & see what answers which you can turn up.
- Also, do some online searching about the key, active ingredients in the stripper; on Wikipedia, Google, & elsewhere.

What, dare I ask, is behind the burning need to get the inside of your chain locker stripped absolutely bare?
Even if you're repainting the inside of the locker, which I can't see as a necessity, as long as the surfaces are clean & well roughed up, the new paint should stick fine.


A few other tools, in particular, for areas where a grinder can't get to, are:
- A wire wheel (mounted in a drill)
- Products akin to this, Wagner 4-1/2 in. Paint Eater Replacement Disc-0513041 - The Home Depot which fit into a drill's chuck, & do an amazing job of stripping; paint, rust, etc.
They're just a very tough, fibrous, synthetic material, designed for stripping. Which work very well. I can't vouch for the Wagner version, although it looks very much like the one's which I've chucked into my drill over the years.
- Option #3 would be to use a drill attachment, which has a large number of sandpaper flaps, mounted on a center spindle, which fits into the chuck of a drill.
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Old 30-06-2015, 05:32   #6
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Re: methylene chloride to remove interior paint from hull

Thanks for the information on alternatives. I'll look at those. I need to get rid of the paint because i'll be doing fiberglass work up there.
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Old 30-06-2015, 06:29   #7
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Re: methylene chloride to remove interior paint from hull

Ready Strip is one that comes to mind. I used it to remove bottom paint and did not affect the gel coat. There are others such as Aqua Strip, etc.
Unrelated are Raven, Darlene, Chantel, etc... You get very interesting results when you Google strippers.
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Old 30-06-2015, 06:35   #8
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Re: methylene chloride to remove interior paint from hull

Methylene Chloride (Dichloromethane - DCM):
Cured polyester resins will not really dissolve in organic solvents like acetone or methylene chloride, but will soften and swell after a time, and eventually break up and crumble.
Methylene chloride is a more aggressive solvent than acetone, but would still take a few days to break the resin up, if the resin was well cured.
On the slightly inhibited back face of a laminate you would get an almost instant reaction as the solvent dissolved any wax and undercured resin, but once this top layer was removed, it would take some time for the solvent to damage the underlying resin.
74 ➥ Fibreglass FAQs - East Coast Fibreglass Supplies
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Old 30-06-2015, 06:51   #9
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Re: methylene chloride to remove interior paint from hull

One thing I forgot to mention is that when you use paint strippers, you'll need to wash it off then use a neutralizer before repainting. Give some thought on how you'll remove the runoff. You can use a wet/dry vacuum to clean it up but better to start with an environment friendly product.
Not as aggressive (fast) as the "chemical" ones, but they will do the job.
I know your pain as this is a part of the boat that has obtuse corners and sometimes very hard or impossible to sand.
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Old 30-06-2015, 09:06   #10
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Re: methylene chloride to remove interior paint from hull

Dry ice media blasting,google for dealer near you.
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Old 30-06-2015, 10:10   #11
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Re: methylene chloride to remove interior paint from hull

I didn't mean to discourage your use of the methylene chloride on either polyester OR epoxy. I just wanted to strongly reinforce to a less experienced user the potential damage that could result from inattentiveness. Gord is correct (sorry, UNCIVILIZED) about the rate of attack. I have used Jassco stripper for many decades to remove linear polyurethane paint from epoxy substrates, with no issues. You just have to pace yourself so as not to leave the stripper longer than necessary, or to use more than is required. Be conservative and cautious, especially when working on a vertical surface. When the material has bubbled up, strip it off with a wide-bladed putty knife, then wipe up the damp remainder with rags (you WILL be wearing protective gear or you won't be doing this work for very long - it burns like acid on your unprotected skin). After it air dries, you can sand it to get a clean, smooth substrate for your primer or paint. Washing it with water is also a good practice. Just remember, this is not something that you want to do in large enough quantities to kill off the critters swimming beneath your boat. Be mindful.
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Old 30-06-2015, 10:13   #12
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Re: methylene chloride to remove interior paint from hull

I just finished a major stripping job, decks and cabin top on a Bristol 40. I used Ultra Strip from Jamestown Distributors. It's not toxic, almost no odor and works really well. I put it on thick and then covered it with cheap disposable plastic drop cloths to keep it from drying out. The waited 24 hours, alot of the paint came up stuck to the plastic sheeting. There was probably 8-10+ layers of paint on everything, and it al came off with two to three applications of stripper. I did scrape between applications and of course had to sand and fair afterwards, which you would expect to do anyway.
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Old 30-06-2015, 11:05   #13
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Re: methylene chloride to remove interior paint from hull

3M makes a product called Safe Stripper. It is non-toxic and water based. You can get it at Home Depot. Brush it on and then cover with Saran wrap or other similar household plastic wraps to keep it moist. Close the locker to help keep area from drying out. Wear gloves as it's messy when you remove it. Keep a spray bottle with water handy. Wipe off with paper towels and then use a nylon scouring pad to scrub it off the remainder. No fumes! Depending on thickness of paint coats it may take multiple applications. Rinse when done. It will not hurt wet / dry vac when you remove the water from the locker.
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Old 30-06-2015, 14:27   #14
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Re: methylene chloride to remove interior paint from hull

remove mechanically with a very stiff wire brush and then oven cleaner will take off the paint without touching the resin. Methylene chloride is very toxic in close quarters and will at the least require a fan and organic chemical mask. I have used the chemical stripper to remove the resin from a lamination in a short amount of time by putting it on and after 15 minutes
it is soft enough to wire brush the resin out of the glass fiber leaving them exposed for the new work to bond to.
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Old 30-06-2015, 17:25   #15
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Re: methylene chloride to remove interior paint from hull

There is a stripper called "AIRCRAFT STRIPPER". It is sometimes sold at automotive supply stores. It is what is used for stripping fiberglass cars such as Corvette. You could haunt some of the Corvette forums as well.


I would not use the stripper you suggested. I know it can damage your fiberglass. Chlorinated hydrocarbons are aggressive to cross linked resins; epoxy, polyester, vinyl ester in varying degrees. I worked for DOW for 20 years - I know this.


I am not so picky about perfection inside a locker. I use a good degreaser such as lacquer thinner or acetone and then paint using Sherwin Williams 2-part white epoxy industrial tank water-proofing. I think this is about equivalent to pool paint. They have two grades; really fast and bloody stinking fast. I use the slower one diluted with acetone. Only mix as much as you can apply in 15 minutes. It sticks to everything except polyethylene. This stuff is way lower cost than marine store paint.
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