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  Muriatic Acid to Restore tired Gelcoat?

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Author Topic:   Muriatic Acid to Restore tired Gelcoat?
rubadub555 posted 07-16-2002 10:26 PM ET (US)   Profile for rubadub555   Send Email to rubadub555  
Friend of a friend reports using muriatic acid on a brush to restore his Whaler's gelcoat to like-new sheen, then waxing to protect.
I used this acid to spot-clean some stubborn rust stains,and it DID shine up the area, but I wonder about the advisability of application to the whole hull. Any opinions?
Boston Marine posted 07-16-2002 11:44 PM ET (US)     Profile for Boston Marine    
Old Whaler 13,oxidized bad,audible pits in gel when passing hand on surface.No shine on upper surfaces whatsoever. I removed every stitch of hardware from this boat then placed in my homemade jig for rolling boat over.
Step 1:DA (Dual ACtion) sander with 600 3-M No Load paper to whole boat (Hull bottom included)to bring the peaks off of gel down level with pits.(Hookit Discs+ DA)
Step 2:Use 800 paper, same idea. (Hookit)
Step 3: Use 1200 paper Same idea. (Hookit)
Step 4:Use 1500 Paper (DA+Wet) (Hookit)+Spray bottle loaded heavy with Ivory soap.
Step 5: Use 2000 paper (wet& by hand using medium hard rubber foam block backer)Sand one direction only..
Step 6: 3-M T-Cut Compound using air buffer.($ 37.00 Quart)
Step 7: 3-M Swirl Remover using air buffer.($28.00 Quart)
Step 8 3-M Finesse II using air buffer.(27.50 Quart)
Step 9: Power buff three coats Mothers Pure carnuba into gel coat.
Result?= The boat turned out to be as smooth and level as a plass plate! Literally.This boat is better than new as far as shine, level of gel etc.No ripples in gel.Towels just slide off when placed on slanted parts of hull.Reflections are true and straight to form.I could shave using as a mirror.
I dont mean to boast but this was the first time I have tried this.I tried to use the same steps as any good body shop would use to finish off a laquer paint job. I refused to use any "Marine Products". Use automotive compounds designed for hard finishes because they cut instead of tear.The marine compounds are too soft and do not cut well.

Time Spent= 80 hours approx including install all hardware.
I just wanted to see if anyone else has tried this vs just re-paint of just buff.

skred posted 07-17-2002 09:20 AM ET (US)     Profile for skred  Send Email to skred     
The only time muriatic acid was recommended to me was to remove dried vegetation/scum from a freshwater hull that had been sitting all summer, then pulled out and the stuff dried onto the hull. It worked very well, and does no harm to the gel, but it doesn't polish it - just dissolves vegetation, etc. Not too easy to work with though: very caustic, and will etch a trailer's finish instantly.
Bigshot posted 07-17-2002 09:46 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Make it shiney......not from my experience. I use it to remove rust stains and algae growth. If anything it makes it dull.
Highwater posted 07-17-2002 09:57 AM ET (US)     Profile for Highwater    
Just to reiterate what Bigshot and others have said, if the hull is brown with water stains (i.e., it has a "beard"), or if it has rust stains, use muriatic acid )or toilet bowl cleaner) to do the initial cleaning. After you have put it on (with rubber gloves), let it sit for 2-3 minutes then wash it off. Thoroughly! Repeat if necessary. Then remove the oxidation, polish, and wax the hull as outlined above and in other posts. If the hull is in especially bad shape, it is always fun to take a before and after photograph. Cheers!
jameso posted 07-17-2002 10:08 AM ET (US)     Profile for jameso  Send Email to jameso     
I have used Barkeepers Friend to remove rust stains, it has oxalic (sp) acid in it, it is also abrasive.
Jim Armstrong
whitefoot posted 07-17-2002 02:16 PM ET (US)     Profile for whitefoot  Send Email to whitefoot     
Muriatic acid is some nasty stuff. We used it when I cleaned pools many lifetimes ago. I have been around some nasty chemicals, but something about the smell of Muriatic acid always gets me. Make sure you keep it away from your metal fittings, especially brass, even if it is chromed. I tried to use it to clean some gunk off a chromed brass fitting one time and before I knew it all I had was a chrome shell of my fitting. The brass had been completely eaten away.

A local (Lafayette, LA) boat finish restorer recommended a product called FSR(Fiberglass Stain Remover) to me. I used it to remove rust spots and it worked very well. Brush it on, let it sit and rub it off. Available at most boat shops around here and West Marine.

Highwater posted 07-17-2002 02:40 PM ET (US)     Profile for Highwater    
Good point. Forget the muriatic acid. The FSR works fine and is safer.
bsmotril posted 07-18-2002 09:57 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
I second the FSR. It is a gel easily painted on with a disposable foam brush. But, the acid in it will do a number on your galvanized trailer. Protect your trailer, or IMMEDIATELY? hose off any drips. Otherwize you'll have white zinc oxide freckles on your trailer. PS, this stuff also works great on fiberglass bathtubs that might have gone a bit too long between cleaning while the wife is out of town.
Highwater posted 07-19-2002 11:41 PM ET (US)     Profile for Highwater    
I have never used muriatic acid on gelcoat--I was thinking of the acid in toilet bowl cleaner, whatever that is. I agree that there is no reason to put muriatic acid on gelcoat when there is a safer, less toxic product that will return brown gelcoat to its original color.
Boston Marine posted 07-20-2002 02:03 AM ET (US)     Profile for Boston Marine    
As I recall you asked how to restore sheen or AKA shine. The reason that gel becomes dull is that it pits due to the sun. In order to restore shine,sheen or whatever you want to call it is to level the gel out. That means,level out the peaks to pits. Then and only then can you hope to get a great shine.Compounds just tear gel and fill the microscopic pits. Then you have the illusion of a shine for a couple of weeks untill the sun erodes the compound residing in the pits.
My 1,000,000 Worth.
kingfish posted 07-20-2002 09:18 PM ET (US)     Profile for kingfish  Send Email to kingfish     

With all due respect, is that thing about "tearing" the gelcoat and some basic difference between marine and automotive rubbing compound something you have witnessed microscopically, or is it just something you have heard or read somewhere?


Boston Marine posted 07-20-2002 09:22 PM ET (US)     Profile for Boston Marine    
I know this for a fact-Try the two methods and see which one turns out better

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