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15-12-2017, 22:06
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#1
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Registered User
Join Date: Feb 2014
Location: Mcleans Ridges NSW Australia
Posts: 25
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Acid washing topsides of GRP boat
A broker told me of a boat that's been refitted to look like new. He went on to say that the topsides were acid washed then polished and they are "gleaming".
I was of the opinion that acid washing fibreglass boats damages the gelcoat.
Any comments would be appreciated.
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15-12-2017, 23:46
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#2
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Senior Cruiser
Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 12,113
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Re: Acid washing topsides of GRP boat
Muratic acid
It cleans off all of the oxidation. Then you just rewax it
__________________
Non illigitamus carborundum
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15-12-2017, 23:55
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#3
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registered user
Join Date: Dec 2012
Location: back in West Australia
Boat: plastic production boat, suitable for deep blue water ;)
Posts: 1,088
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Re: Acid washing topsides of GRP boat
When I was working with fibreglass we made tanks to hold very strong acids. But as you may know there are many different kind of resins around. Some better than others.
here is a link at random: Storing Sulfuric Acid Using Fiberglass as a Material of Construction - Beetle Plastics
Damaging gelcoat? Doubt it, but firstly of course depends what acid is used. I think the common ones for cleaning are Oxalic acid, Phosphoric acid and Citric acid. For cleaning purposes on boats, I have only used the former one.
In my view, they do not affect the gelcoat at all. Yes these acids will remove any wax that is on the hull. The acid may leave some white residue, if the cleaned parts are not properly rinsed. These acids remove rust stains and the brown 'haze' close to the waterline.
As the diluted acid drips down the hull (ie from the deck, rigging, or railing) they drip then onto and along the antifoul. The antifoul can then show whitish streaks. In theory it may reduce the effects of the antifoul, but in practice, I have never noticed diminished efficiency of the antifoul.
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16-12-2017, 05:32
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#4
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Registered User
Join Date: Dec 2009
Boat: JBW club 420, MFG Bandit, Snark
Posts: 871
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Re: Acid washing topsides of GRP boat
Quote:
Originally Posted by HankOnthewater
As the diluted acid drips down the hull (ie from the deck, rigging, or railing) they drip then onto and along the antifoul. The antifoul can then show whitish streaks. In theory it may reduce the effects of the antifoul, but in practice, I have never noticed diminished efficiency of the antifoul.
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Diluted is the key word here. I wouldn't go at a boat with full strength acid. I do smaller sections at a time so the acid isn't on their too long.
I've acid washed my bandit and 420 several times. Makes them look great every year, like I keep them under a shelter and take care of them. They actually look like they don't spend summers on the shore behind the house and winter's under some pine trees, uncovered at all times.
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I love big boats and I can not lie.
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16-12-2017, 05:43
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#5
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Registered User
Join Date: Feb 2006
Posts: 2,767
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Re: Acid washing topsides of GRP boat
Quote:
Originally Posted by newhaul
Muratic acid
It cleans off all of the oxidation. Then you just rewax it
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YEP those toilet bowl cleaners
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16-12-2017, 07:17
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#6
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Registered User
Join Date: Feb 2013
Location: Bumping around the Caribbean
Boat: Valiant 40
Posts: 4,625
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Re: Acid washing topsides of GRP boat
Mary Kate ON/OFF is nothing but acid. Super at cleaning gelcoat, including getting rust stains out. You dilute it pretty aggressively. Pretty much every yard I've been to uses it or it's equivalent to clean decks.
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16-12-2017, 07:49
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#7
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Registered User
Join Date: Mar 2007
Location: Santa Cruz
Boat: SAnta Cruz 27
Posts: 6,683
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Re: Acid washing topsides of GRP boat
Older gelcoat gets porous, and picks up a brown mustache from things like tanin in the ICW. The fix is to acid wash with oxalic and then fill the pores with wax. Repeat as often as needed.
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16-12-2017, 08:21
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#8
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Senior Cruiser
Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 12,113
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Re: Acid washing topsides of GRP boat
Quote:
Originally Posted by geoleo
YEP those toilet bowl cleaners
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muratic is an ingredient in many crapper cleaners. I purchase mine full strength by the gallon.( cleans the dink of barnacles really good to.)
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Non illigitamus carborundum
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16-12-2017, 08:38
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#9
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Registered User
Join Date: Jan 2010
Location: Portland, Oregon, USA
Boat: 31' Cape George Cutter
Posts: 3,270
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Re: Acid washing topsides of GRP boat
It should be clear from this that while the acid doesn't remove good gelcoat, it does remove the oxidized gelcoat. This in turn sets it up for further oxidation, so over time gelcoat is lost. Acid cleaning without sealing with wax or resin will probably accelerate gelcoat loss, so definitely keep up the seal as much as possible.
Greg
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16-12-2017, 09:33
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#10
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Registered User
Join Date: Mar 2003
Location: Fredericton, NB, Canada in the summer and fall; Caribbean in winter and spring aboard Cat Tales.
Boat: FP Tobago 35 (and a H-21 SE)
Posts: 620
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Re: Acid washing topsides of GRP boat
On/Off is just acid, diluted muriatic, I think. It is almost necessary for getting waterline tannin off white hulls before waxing. I do have something to add, however. In the islands, when you hire a local to wash and wax or just to wash, in some of the boatyards, what they do is splash muriatic or Ospho, then wax. No elbow grease for them. However, they pit your rubrails, your toerails, your through-hull fittings. We need to specify what can be used, or completely supervise these people.
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16-12-2017, 09:36
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#11
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Registered User
Join Date: Feb 2011
Location: France, britanny
Boat: twinkeels, 9m
Posts: 406
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Re: Acid washing topsides of GRP boat
oxalic acid is not very dangerous, I use it for years
let it bleach the hull few minutes, then rinse thoroughly, polish lightly, and apply a wax.
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16-12-2017, 13:13
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#12
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Moderator Emeritus
Join Date: Sep 2006
Posts: 4,663
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Re: Acid washing topsides of GRP boat
Muriatic acid can be purchased cheaply where swimming pool chemicals are sold. It's really just another name for hydrochloric acid, but when sold as muriatic acid it's usually more dilute.
Oxalic acid can be found as "Wood Bleach" at the hardware store. It's a box of white crystal powder that you mix with water. "Barkeeper's Friend" contains oxalic acid.
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Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
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16-12-2017, 15:08
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#13
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,241
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Re: Acid washing topsides of GRP boat
Quote:
Originally Posted by newhaul
muratic is an ingredient in many crapper cleaners. I purchase mine full strength by the gallon.( cleans the dink of barnacles really good to.)
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What final percentage solution do you use for cleaning gelcoat?
Around here bulk muratic is sold at 33%.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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16-12-2017, 15:25
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#14
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Senior Cruiser
Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 12,113
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Re: Acid washing topsides of GRP boat
Quote:
Originally Posted by Wotname
What final percentage solution do you use for cleaning gelcoat?
Around here bulk muratic is sold at 33%.
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I use it full strength just don't let it get on painted surfaces you don't want stripped clean off.
__________________
Non illigitamus carborundum
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16-12-2017, 15:39
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#15
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Registered User
Join Date: Feb 2014
Location: Mcleans Ridges NSW Australia
Posts: 25
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Re: Acid washing topsides of GRP boat
Hi There
The fibreglass tanks you used to store acids were they made using epoxy resin?
Happy days Sailing
Frank
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