Removing Concrete from hull

solmate · Jul 28, 2011

need help in removing concrete (small spots.... pea to dime size) from hull. Only on port starboard side. Looks like previous owner ran thru wet concrete.. Any ideas or solutions?

rockyrude · Jul 28, 2011

Re: Removing Concrete from hull

I'm not sure which side it's on(or both maybe?) but if on the outside, first use a plastic type scraper to knock off the big pieces and then something like CLR should dissolve the remaining cement it's only calcium anyway right?

boat1010 · Jul 28, 2011

Re: Removing Concrete from hull

Maybe if you gave us a little more infromation we could be of better help.. What is your boat made of?

solmate · Jul 28, 2011

Re: Removing Concrete from hull

It's a 1993 Celebrity bowrider. Dark green fiberglass, concrete is on outside of hull, I have scraped some of the pieces off but the remaining small splatters won't budge. Will CLR hurt the gelcoat? Thanks for the help

boat1010 · Jul 28, 2011

Re: Removing Concrete from hull

CLR should do nothing to the gel coat. After you get done getting off the concrete it might be a good thing to put a little wax on it.. You may have to sand some on it to get some off, then you can buff it smooth. Be careful about that because you may want to do the whole boat...LOL Lots of work..

solmate · Jul 28, 2011

Re: Removing Concrete from hull

thanks for the help, boat is perfect for her age but these spots have been bothering me..... Just another reason to tinker with the boat lol
I'll give the CLR a try

robert graham · Jul 28, 2011

Re: Removing Concrete from hull

If CLR don't get it, and you have a lot of concrete on your hull, buy a gallon of Muriatic Acid from Home Depot, dilute maybe 1/2 with water, apply with a brush, rinse off...that's what masons clean concrete off the bricks with. It's good stuff to have around for a variety of applications like yours. Good Luck!

kcfromohio · Jul 28, 2011

Re: Removing Concrete from hull

Concrete? or is it salt deposits? Has your boat ever been in the ocean? Has it ever been towed through the northeast states where they use salt on the roads to melt ice? I would use a mild water based acid cleaner (zing) and clean and wax the hull.
iboats sells Zing, but you have to buy it by the case. You will probably need a half gallon mixed 70/30 with water. use a garden sprayer to apply and a pressure washer to remove. Be careful not to breath the fumes of the cleaner while you are spraying it on!

solmate · Jul 28, 2011

Re: Removing Concrete from hull

Boat has spent it's entire life in Oklahoma, I know its concrete from prior experience with a dodge truck! Yes, I drove thru wet concrete what a mess. I'm trying the CLR now & will get muriatic acid tomorrow... need some for the pool anyway. As soon as I get the concrete splatters off I plan a good waxing followed by a vaseline treatment

kcfromohio · Jul 28, 2011

Re: Removing Concrete from hull

I would not use muriatic acid. I would recommend using hydrofluoric acid. It will wash off with a strong water rinse. muriatic acid may need to be neutralized after application.

solmate · Jul 28, 2011

Re: Removing Concrete from hull

Thanks to all who've posted.... The CLR is working.... Have a lot of little splatters but it's coming off... The only thing is it's 109 outside & the CLR dries up in seconds. haha. May way & try it early in the morning

Fishing Dude too · Jul 28, 2011

Re: Removing Concrete from hull

I know we used oil to remove from forms when I worked concrete years ago use cooking oil. Let soak for awhile then it should release.

jigngrub · Jul 28, 2011

Re: Removing Concrete from hull

What are all of these acid solutions going to do to the trailer the boat is sitting on, what about the carpet on the bunks?

Concrete is mostly lime, not calcium.

I would suggest a powerful pressure washer (3000 psi) with a turbo tip on the sprayer wand. Test on an inconspicious spot on the boat first. Start at a distance of about 3' to make sure you aren't hurting anything and move closer until you get a good cleaning action.

If you try everything and nothing works, you'll have to very carefully pick the concrete off with a metal putty knife.

In the concrete construction trade we use pressure washers, sharp scrapers, hammers, and chipping/jack hammers to remove concrete that has setup... it doesn't come off easy.

The pressure washer and acid solutions work best on concrete and mortar that hasn't setup completely. I don't think this is your case.

MCFLYIN · Jul 28, 2011

Re: Removing Concrete from hull

Hydroflouric acid???? I didnt know you could buy this stuff retail. Do you know what that stuff can do to you? There is no way in hell I would be messing with hydroflouric (HF). If you get that stuff on your skin above a certain concentration it will immediately melt your skin down to the bone. I 2nd the CLR with a pressure washer.....no way I would mess with HF

jayhanig · Jul 28, 2011