stripping paint Muratic acid

[Glen Lee]

Looking for info on striping paint from 50 + year old fiberglass hull.
Boat is 1960 Rhodes Ranger 29 s/n 4.
There was some discussion on the use of Muratic acid but I cant find it now.

1. general use ok on fiberglass?
2. Dilute to what level?
3. Apply how?
4. Let sit how long?
5. Remove with hose water (~40 psi ) ?
Alternative Hi pressure

6. Your thoughts ?

[Seymore]

Do Not Use Muriatic Acid. Muriatic acid is impure sulfuric acid, and it tends to not dissolve plastics and paint. It tends to dissolve metals. And eyes and skin...

Use marine paint remover and follow the instructions.

I don't know your circumstances. That being said, I would tend to simply sand a 50 year old fiberglass boat carefully and spray (repaint) it.

[Wotname]

Originally Posted by Seymore

Do Not Use Muriatic Acid. Muriatic acid is impure sulfuric acid, and it tends to not dissolve plastics and paint. It tends to dissolve metals. And eyes and skin...

Use marine paint remover and follow the instructions.

I don't know your circumstances. That being said, I would tend to simply sand a 50 year old fiberglass boat carefully and spray (repaint) it.

Not exactly, muriatic acid is hydrochloric acid - HCl; often used for cleaning concrete, bricks etc and in swimming pools.

Sulfuric (sulphuric) acid is H2SO4 is used in lead acid batteries and is quite different to muriatic acid.

AFAIK, neither are suitable for common paint removal.

[GordMay]

Greetings and (belated) welcome aboard the CF, Glen.

[transmitterdan]

For chemical removal first try one of the soy based paint removers. If that doesn't work then try something more harsh. Follow directions religiously.

But the "best" paint removal technique is to use one of the compressed air abrasive removal systems. You can pay someone to come to your boat and remove the paint. Will be less effort than chemical removal and the surface will be already prepped for barrier coat and paint. There are various abrasive materials ranging from walnut shells to glass beads.

Don't use any acid on a fiberglass hull to remove paint. It will attack the resin in the hull and anything metal it touches.

[Suijin]

Assuming that you are talking about bottom paint, chemical stripping can end up being more time consuming and more expensive than any other method, particularly with older paints and very thick paint applications. If you try it, be sure to cover the treated area with plastic and let it sit 24 hours. Do tests with various products before slathering the whole boat with something that does not work.

I tried chemical stripping of 30 years worth of bottom paint on my boat five years ago. Was a pretty fruitless endeavor. The ended up using a carbide scraper and then finish sanding.

Media blasting is great if you plan to barrier coat. Otherwise it usually leaves a pebbled surface that needs to be faired. And it be seen a few horrific media blasting jobs over the years. Operator skill and experience is key to a good job.

[Debgen]

Muratic acid will not dissolve plastic or paint. I often used a 25% diluted mixture with water to clean scum stains and rust marks on both painted and gelcoated surfaces. wear gloves and face protection.

[skipmac]

Originally Posted by Wotname

Not exactly, muriatic acid is hydrochloric acid - HCl; often used for cleaning concrete, bricks etc and in swimming pools.

Sulfuric (sulphuric) acid is H2SO4 is used in lead acid batteries and is quite different to muriatic acid.

AFAIK, neither are suitable for common paint removal.

Correct. Muriatic is a common name for hydrochloric acid HCl.

[JOHNMARDALL]

Definitely don't use acid, it won't remove the paint but will damage everything it touches, especially you. Also, be aware that many marinas and boat yards will not permit DIY removal of bottom paint - the toxic products can be a serious clean up problem. If the yard allows it, paint stripper and a scraper are possible, but after you've worked for eight exhausting hours, hurt your back, covered yourself with toxic muck and removed three or four square feet of that 30 year paint build up, think about getting a quote for blasting with glass beads or other controllable fine abrasive material (not sand) - it will be done in a day, and you'll have a clean, reasonably smooth hull on which to do some light fairing followed by multiple layers of epoxy barrier coat. If you're in the mid-Atlantic, I can give you the contact information for a company who've done excellent work for us.

Good luck
John Mardall
Vetus Maxwell Group

[hellosailor]

"Assuming that you are talking about bottom paint,"
It would be good to confirm that.

[atmartin]

If we are talking bottom paint, I've had good results with PeelAway Marine, even going through 40+ years of bottom paint. It's a lye based stripper that goes on like plaster (I use a trowel) and then you cover it with paper. Pretty clean stuff when you use it right. Usually it just takes some orbit sanding with 80/120 grit after you rinse the hull. Wear goggles and if you get it on your skin, rinse quickly (I use vinegar) because it will burn you. I have a couple of scars from not rinsing the stuff off fast enough.

"This...is chemical burn"

It can take a very long time to remove bottom paint mechanically, plus with chemical stripping you're less likely to ruin the fairness.

[IMACSS]

Thanks for the great thread everyone.

I have a Noelex trailer sailer that had (for some reason) anti-fouling applied that is now at almost down to about 50% coverage and looks awful. Best part that I can think of is that the epoxy applied under the coating is protecting the original gelcoat. May have trouble one day convincing an interested buyer I guess.

Either way I am going to remove the anti-fouling one day and make its bum shine again.

[transmitterdan]

If it is epoxy under the paint you need to keep it painted. Paint protects the epoxy from the sun.

[lituya1617]

If taking off bottom paint with HCl does not work, why do marina's prohibit it? Could it be related to the fact that marinas sell blasting service to remove bottom paint? Also, why do all paint manufacturers say that HCl is a good paint remover for wood, brick, concrete, etc.? HCl is a common way to clean the paint, oils and surface gunk from concrete. If HCl takes paint off wood, brick, concrete and everything else, why not fiberglass? As to whether HCl harms gel coat, how does that occur? Polyesters and vinylesters are very acid resistant. HCl will take off surface waxes but should not harm the gell coat itself. Please give me some references to back up these claims.

[S/V Illusion]

Originally Posted by lituya1617

If taking off bottom paint with HCl does not work, why do marina's prohibit it? .

Wrong ‘tool’ for the job. If you want to chemically remove paint, solvents are the correct choice. Marinas are required to adhere to best management practices and indiscriminate use of acidic liquids can be much more harmful than most volatile solvent based strippers. There is no conspiracy here.