Painting v Oxalic acid

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alant

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I notice a couple of threads on use of Oxalic acid, to clean/renew a faded/stained hull.

Should this fail, apart from going to a yard to get it done professionally, what would forumites recommend for a simple hull 'paint' job. Someone I know, with little previous experience of maintaining a boat, has been quoted over £600 by a local yard (+ materials), for painting the hull of his 22' boat (which was built in 70's & not of great financial value). I remember some guys successfully painting their racing dingies, with 'Woolworth' paint, so is there a viable alternative to the 'marine' products,to paint GRP?
 
Painting is said to be "90% preparation, 10% application". Hence the cost of a professional job. The cost of good quality materials is a relatively small proportion of the total if durability is required.
DIY painting is entirely feasible, but time consuming for preparation if a good standard is sought.
A lick of paint on a dinghy at home is not quite the same as painting a cruising boat in a yard.
I don't think oxalic acid will improve a faded gel-coat.
 
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Plenty of information on the websites of paint manufacturers. Series running in PBO on exactly this subject repainting an old 22 footer! £600 is reasonable for the job using conventional paints such as Toplac or Hempels enamel. Materials will be around £100 and the rest will be labour, probably 10-15 hours.

Quite possible to DIY. The PBO one is starting from a very poor substrate so lots of filling and fairing. They are doing the whole boat which would not be necessary if it is just the hull that needs freshening up. Many old hulls respond well to a thorough clean and provided you recognise that you will never get a showroom finish will still look good on the water.
 
alant said:
I notice a couple of threads on use of Oxalic acid, to clean/renew a faded/stained hull.
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A better option and less toxic is acetic acid available in powder/crystal form from brewing shops, does the same job as oxalic. It is also very effective at removing tools (drills/tapps) that have sheered off in Stainless as the acid corrodes the carbon steel but not the SS.
 
I would resist painting GRP until all other options had been tried; once you paint it, you need to do it again, and again ...

My garage door at home has been in its original primer for 20 years, and although the colour is a bit naff, it still looks smart. In my last house I had to repaint the door every year. A no brainer.
 
Neil_Y said:
A better option and less toxic is acetic acid available in powder/crystal form from brewing shops, does the same job as oxalic. It is also very effective at removing tools (drills/tapps) that have sheered off in Stainless as the acid corrodes the carbon steel but not the SS.
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Acetic acid is not a solid, at least not at room temperatures. I'd doubt if its available from brewing shops.

Perhaps you were thinking of citric acid.
 
I agree that it is better to avoid painting a grp hull; try cleaning it instead. However, if you decide to pain the hull, use good marine paint (eg International; expensive but goes long way) prepare the hull well, use sponge brushes for smooth finish and choose a still warm day. for a 22ft hull it will take 3 hours to prepare and paint each side; say one day for the whole boat, tops. The results will be good and the hull will not need to be painted again for at least 7 years.
 
CAPTAIN FANTASTIC said:
... for a 22ft hull it will take 3 hours to prepare and paint each side; say one day for the whole boat, tops. The results will be good and the hull will not need to be painted again for at least 7 years.
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That's what I thought. Here's how it went on my Snapdragon 24:

Fill and sand a load of little digs and scratches
Prime hull

Do
......Fill and sand all the bits you missed.
......Reprime Hull
Loop until pissed off with the whole business

Final light sand
Top Coat
Flatten with 400 wet & dry
Final Coat.

The bit about 7 years sounds about right, though. Could be longer if you use a quality 2-pack paint & don't biff the poor thing against the pontoon.

The secret really is the preparation. I saw a few 3 hour Dulux jobs when looking for a boat I could afford :eek: .
 
Painting a boat often means that someone is covering damage, It may reduce the saleability of the boat.

Agree with painting only as a last resort. Never use single pack paint unless the boat is pretty worthless in the first place.

I'd try cutting back/polishing the grp and applying a uv polish/sealer...... if there really is such a thing.
 
As said if the hull is undamaged and simply faded or stained. Use acid first then try a cut type polish not silicon.
If however there is damage scratches etc then the only way to fix is a whole paint job. I used a 2 pack polyurethane in white. I just brushed it on. Not brilliant close up but from a distance it looks good. The thing being you can always touch up the paint over damage which to me is inevitable. So I have been able to keep my boat smart if not immaculate for about 20 years since first paint job.
So try to avoid paint but eventually you will have to go for it. good luck olewill
 
William_H said:
If however there is damage scratches etc then the only way to fix is a whole paint job.
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NO! Has Western Australia no capable crafts people? :)

I had quite a lot of gel and strand mat damage (beneath the gel) during the summer due to my anchor breaking loose and it chewed away for nearly half an hour before conditions were safe enough to tame.

This was repaired plus any other scratches. The repairs are not visibly different to the original gel. Repairs + an all over polish afterwards (33 footer) cost me £300

S.
 
Scotty_Tradewind said:
NO! Has Western Australia no capable crafts people? :)

I had quite a lot of gel and strand mat damage (beneath the gel) during the summer due to my anchor breaking loose and it chewed away for nearly half an hour before conditions were safe enough to tame.

This was repaired plus any other scratches. The repairs are not visibly different to the original gel. Repairs + an all over polish afterwards (33 footer) cost me £300

S.
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If cutting back, unless the gel is of 'substantial' thickness, there is always a possibility, that you get down to the strands. Also, if hull is deep cleaned, needs to be coated with something, to stop any gelcoat acting as a microscopic sponge & becoming dirty again, so application of some 'polish' presumably must be used, even if its Mr Sheen!;)
Like the comment about paint 'hiding' problems, will pass that on.
 
Neil_Y said:
You're right Vic, why did I type Acetic???
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1ac in today's DT Xword.

For minor rust and brown stains acetic acid in the form of vinegar does a fair job. Similar mechanism to that of oxalic acid but not as aggressive. Brown sauce as a poultice also works, will be applying some today to that irritating rust run from the anchor well drain.
 
Scotty_Tradewind said:
NO! Has Western Australia no capable crafts people? :)

I had quite a lot of gel and strand mat damage (beneath the gel) during the summer due to my anchor breaking loose and it chewed away for nearly half an hour before conditions were safe enough to tame.

This was repaired plus any other scratches. The repairs are not visibly different to the original gel. Repairs + an all over polish afterwards (33 footer) cost me £300

S.
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A few crafts men around here. But I would not let them at my boat. Like 30 years ago the builder of the first sail boat to take the Americas Cup off the Americans in 132 years. IMHO a polyester resin (gel coat) is not the best material to cover scratches etc on an old fibreglass boat. it was quite fine for your extensive repairs where the last coat with pigment (gel coat) was applied to a green substrate such that a good chemical bond occurred. However where you are looking for a layer to match the original gel coat then more gel coat is not the best at adhering to the original hull. Even though it was the original material. Yes it might stick OK and you might get the colour correct but it is paint that is chosen because it sticks well to all sorts of substrate. Polyurethane (2 pack paint) is a resin that has very good adhesive qualities is very hard and UV resistant.
Then there was a friend many years ago who bought what he thought was correct colour gel coat to repair some scratches. He wondered why it did not go hard when he added hardener. Turned out it was a pot of pigment with not resin in it at all.
good luck olewill
 
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