How To Remove Concrete From Gelcoat?

[JaSla74]

Here's one fur ya. How would you suggest going about removing concrete splatter from gelcoat? I assume the previous owner was mixing some concrete a little too close to the boat at one point. I've purchased some Dupont 606s compound and am getting ready to clean up my hull, but am perplexed as how to remove this. Thoughts?

 

[ondarvr]

Re: How To Remove Concrete From Gelcoat

Re: How To Remove Concrete From Gelcoat

Try a plastic ice scraper first and be gentle, if that doesn't do the job, try some muriatic acid mixed 50/50 with water. Wear gloves and other protective gear when using the acid.

Rinse well with water immediately after the acid treatment.

 

[jnorswor]

Re: How To Remove Concrete From Gelcoat?

maybe something that removes calcium build up on faucets, like CLR, would work. I am not sure how you would be able to soak the spots. but anything that attacks calcium carbonate would work.

 

[cbavier]

Re: How To Remove Concrete From Gelcoat?

JaSla: When you get it cleaned off let us know how you did it. First time I have heard of this kind of problem. Whatever you use try it in a inconspicuos area first if you can.

 

[woosterken]

Re: How To Remove Concrete From Gelcoat?

how about WD 40 let soak down behind it?
it has 1001 uses this mite be 1002

woosterken

 

[*EdC*]

Re: How To Remove Concrete From Gelcoat?

Take it to the self serve car wash and use their pressure washer.

 

[reelfishin]

Re: How To Remove Concrete From Gelcoat?

I had an aluminum boat that had the same problem, only a lot worse. It looked like they dropped a bag of Quickcrete on the hull and let it get rained on.
There were 4" sections covered in thin concrete. I tried everything, the only thing that worked as to take a sharp edge and lots of water and chip it off at a sharp angle. It came off with little to no noticeable damage but took several hours. There's not much that will dissolve concrete. If you lucky, it wasn't a thorough mix and may not be fully bonded.

The key is lots of lube and keep flushing away what you have already broken free so as not to scratch the surface.

 

[Tail_Gunner]

Re: How To Remove Concrete From Gelcoat?

Umm you could just get yourself a big old rubber headed sledge hammer and give her a whack of two.... Actually some gentle nudges from a rubber hammer might just brake the bond..im sure it is not that strong of a bond????..Umm that's from the inside..not out.

 

[ebry710]

Re: How To Remove Concrete From Gelcoat?

Acid based compounds remove the calcium and breakdown concrete. That is why they use muriatic acid to whiten concrete.

 

[JaSla74]

Re: How To Remove Concrete From Gelcoat?

WD40 didn't work, although amusing. Plastic scraper didn't work. I couldn't bang from the inside with a rubber mallet, but did bang aroundish it. Only thing that did was leave black marks. I let some compound sit on there for quite a spell and it seemed to loosen it up a bit, but couldn't tell for sure.

In the end I found a screw driver & large allen wrench worked best. I liked the allen wrench, because it's workable without sharp corners. I was super careful and didn't leave any lasting marks. I'm not so sure I'd try this on a high dollar rig, but mine is 20+ year old. I'm gonna try to get my boat on the water for a test run tomorrow and after that I may try the high power car wash.

 

[cbavier]

Re: How To Remove Concrete From Gelcoat?

WD40 didn't work, although amusing. Plastic scraper didn't work. I couldn't bang from the inside with a rubber mallet, but did bang aroundish it. Only thing that did was leave black marks. I let some compound sit on there for quite a spell and it seemed to loosen it up a bit, but couldn't tell for sure.

In the end I found a screw driver & large allen wrench worked best. I liked the allen wrench, because it's workable without sharp corners. I was super careful and didn't leave any lasting marks. I'm not so sure I'd try this on a high dollar rig, but mine is 20+ year old. I'm gonna try to get my boat on the water for a test run tomorrow and after that I may try the high power car wash.

JaSla: After you get the concrete all off. Go to your local Marine store and buy a bottle of 3M Marine Fiberglass Cleaner and Wax #09009 and follow the instructions on the bottle to remove all those little scratches and restore the finish to before concrete condition or even better. "Chuck's Fiberglass"