Oxalic acid working temperature

[MikeBz]

Our (GRP textured) decks are covered in stains from the annual autumnal bird poo festival. Normally the stains start off purple and fade away/disappear quite quickly. This year they are brownish and persisting. I’ve scrubbed and scrubbed to no avail.

I’ve tried a weak Oxalic acid solution, no effect. Have read that Oxalic acid “doesn’t work at low temperatures” but what is “low” in that context? I could use warm water but that will be cooled to ambient almost as soon as it hits the deck.

 

[PaulRainbow]

Our (GRP textured) decks are covered in stains from the annual autumnal bird poo festival. Normally the stains start off purple and fade away/disappear quite quickly. This year they are brownish and persisting. I’ve scrubbed and scrubbed to no avail.

I’ve tried a weak Oxalic acid solution, no effect. Have read that Oxalic acid “doesn’t work at low temperatures” but what is “low” in that context? I could use warm water but that will be cooled to ambient almost as soon as it hits the deck.

It seems to me that if you mix it with cold water it doesn't work as well as with hot water, even if the how solution cools down.

I'm also not sure how well it works on bird poo, perhaps bleach would be a better solution. I use a 50/50 solution of thick bleach (Lidl W5) in some places and it works really well, have also used it neat for smaller stains.

 

[ChromeDome]

Oxalic acid is a bleach, found in rhubarb. Hence care needs to be taken with coloured gelcoat.

As with most chemical products temperature is important. Ever tried dishwashing in cold water?

If ambient temperature is low, warm/hot water can be used when dissolving and applying the oxalic acid.

Oxalic concentration:

• Bleaching/de-greying of wood: Make a 20% solution (200g Oxalic acid in 1 litre of warm water).
  • Apply the solution to the item with a sponge or brush and leave to dry.
    • After drying, sweep the wood and wash with cold water.
• Cleaning of aluminium: Boil 1 tsp. Oxalic acid in 1 l water is boiled in an aluminium pot or similar.
  • Rinse well with water.
• Glass fibre - yellow and dull: Make a 10-20% solution (100-200g Oxalic acid dissolved in 1 l water) and clean the glass fibre thoroughly (rub it in) with the mixture.
  • Rinse with water.
• Rust on clothing, concrete tiles, plastic and fibreglass: Make a 10% solution (100g Oxalic acid dissolved in 1 litre of water).
  • Dab or rub on the rust stain.
    • Wash the area with water afterwards.

The longer you leave it to work/the number of layers you put on, the more bleaching effect.

Nitrile gloves and ventilation are recommended!

 

[Pye_End]

Have read that Oxalic acid “doesn’t work at low temperatures” but what is “low” in that context? I could use warm water but that will be cooled to ambient almost as soon as it hits the deck.

Y10 doesn't do a good job in February temperatures, but does things improve towards spring, so I am guessing sub 10 is a waste of time, 12 to 15 and you have a reasonable chance, over 15 is fine. Just based on experience. Some sun on the boat helps, though also dries it quicker so you can't leave it on so long.

As Paul says, it may be that it is the wrong mixture for bird poo - might be the cause of your problems.

 

[davidmh]

I thought it states on the Y10 box do not use below 10 Deg C. I have found that this is true.
David MH

 

[Baggywrinkle]

I found that application at room temperature or above in bright sunlight works best - removes organic and rust stains very quickly. Performance drops off to almost nothing in the depths of winter.

I use crystals mixed with warm water and a bit of washing up liquid to make it stick to vertical surfaces, made as strong as your protective clothing will allow and applied outside if at all possible.

I also use a pressure washer at close range first to remove any residue from whatever created the stains, but be careful of seals around deck fittings/windows.

 

[wallacebob]

To make a strong solution you need hot water. As the water cools, you’ll get crystals reforming. Use in warmer weather gives best results, although I brightened my woodwork last week. Sunlight aids lightening.
For bird stains I use Aldi patio cleaner in Spring (out of water), it works slowly, and needs sunlight I believe to be fully effective.

 

[MikeBz]

Thanks to all for very useful tips and info. I went back to the boat today and the bit I’d done on Weds actually looks pretty good now, much better then when I rather despondently gave up and left it. I’ll persevere with a stronger solution in hot water and then try bleach or Patio Magic on any remaining stubborn avian ordure stains.

 

[Refueler]

Oxalic acid is a bleach, found in rhubarb. Hence care needs to be taken with coloured gelcoat.

As with most chemical products temperature is important. Ever tried dishwashing in cold water?

If ambient temperature is low, warm/hot water can be used when dissolving and applying the oxalic acid.

Oxalic concentration:

• Bleaching/de-greying of wood: Make a 20% solution (200g Oxalic acid in 1 litre of warm water).
  • Apply the solution to the item with a sponge or brush and leave to dry.
    • After drying, sweep the wood and wash with cold water.
• Cleaning of aluminium: Boil 1 tsp. Oxalic acid in 1 l water is boiled in an aluminium pot or similar.
  • Rinse well with water.
• Glass fibre - yellow and dull: Make a 10-20% solution (100-200g Oxalic acid dissolved in 1 l water) and clean the glass fibre thoroughly (rub it in) with the mixture.
  • Rinse with water.
• Rust on clothing, concrete tiles, plastic and fibreglass: Make a 10% solution (100g Oxalic acid dissolved in 1 litre of water).
  • Dab or rub on the rust stain.
    • Wash the area with water afterwards.

The longer you leave it to work/the number of layers you put on, the more bleaching effect.

Nitrile gloves and ventilation are recommended!

Oxalic Acid is a "dicarboxylic acid" .... not a Bleach. But correct that it is extracted from such as Rhubarb. But most Oxalic Acid nowadays because of the widespread use of - is synthetic ....

"The formula of oxalic acid is (C2H2O4); its usual form is that of the crystalline hydrate, (COOH)2·2H2O. Known as a constituent of wood sorrel as early as the 17th century, oxalic acid was first prepared synthetically in 1776. It is manufactured by heating sodium formate in the presence of an alkali catalyst, by oxidizing carbohydrates with nitric acid, by heating sawdust with caustic alkalies, or by fermentation of sugar solutions in the presence of certain molds."

It also is produced by most mammals naturally but at low levels.

But its action is similar to bleaching ....

Have never had any problem with coloured Gelcoat - except where parafinnic base is used..... for the boater - not really a concern.

I have found that even when wallpaper paste added to help keep in contact with area to clean - the concentration needed is far higher than the 100 - 200g per litre ... I usually keep adding until saturation level when no more dissolves .... in hot but not boiling water.

 

[Ribtecer]

I find Oxalic Acid gives amazing results in the yard and the hull looks brand new with very little work.

But once back in the water the yellowing brown marks return almost immediately.

Am I doing something wrong?

 

[MikeBz]

I find Oxalic Acid gives amazing results in the yard and the hull looks brand new with very little work.

But once back in the water the yellowing brown marks return almost immediately.

Am I doing something wrong?

I don’t think so. When you apply it it “bleaches” (careful use of quotes) the stains which are there, then you wash it off. I would think that to delay further staining you need to ‘seal’ the surface with a wax or maybe some fancy ceramic treatment (now there is another subject).

 

[Sandy]

I find Oxalic Acid gives amazing results in the yard and the hull looks brand new with very little work.

But once back in the water the yellowing brown marks return almost immediately.

Am I doing something wrong?

You are not polishing and waxing the surface.

 

[Ribtecer]

You are not polishing and waxing the surface.

Thanks for the reply/help.

I did I spent alot on a couple of Meguiar's Marine High Gloss Boat Polish.

If there is something better I should use, I'm very happy to repeat the process.

Thanks again.

 

[Sandy]

Thanks for the reply/help.

I did I spent alot on a couple of Meguiar's Marine High Gloss Boat Polish.

If there is something better I should use, I'm very happy to repeat the process.

Thanks again.

People I know speak highly of Meguiar polish, but you need wax to protect the hull.

Each time you apply oxidic acid it removes all the layers of wax.

 

[Refueler]

Years ago - guy I knew used to 'wax' his car and boat with Beeswax .... he spent hours at it ....

Did I ever see any different results ... initially brilliant shine ... but soon after same old crap as anyone else ...

I don't know if its still out there - but a Yard I knew (as a kid did some work in there ... ) - they used a car based polish that was called something like 'Diamond Hard' ... the advertising in those days was a bit 'ott' but - said that showrooms used it for long lasting shine ...
It was not like normal car polish ... which I'm told you should not use - as it yellows ?? But it was like a gloss lacquer barrier.

Me - having tried so many different products ... I use Oxalic to clean ... T-Cut to restore shine to any faded areas (even though its recc'd not to !) ... then a simple carwash with wax included.
Other boats I see use various 'Marine' products and do I note any real difference during the season .... no.

 

[Supertramp]

I use carnauba wax on the car (once per year) and on the boat. It's better than proprietary waxes. I think my boat one is Meguiars Carnauba wax.

 

[Ribtecer]

People I know speak highly of Meguiar polish, but you need wax to protect the hull.

Each time you apply oxidic acid it removes all the layers of wax.

So polish by itself doesn't do the job?

Thanks. I'll get some wax, any product recommendations gladly received.

Shame, I put 2 coats of the Meguiar polish on.

 

[Fr J Hackett]

Oxalic acid works by converting stains usually iron or similar metal based insoluble stains into soluble ones which can be easily washed away, it maybe that the bird poo and stain is largely organic and thus the oxalic acid is ineffective. Like all chemical reactions the conversion of say iron oxide to the soluble oxalate is temperature dependant, basic thermodynamics, it is also very dependant on concentration which is more effected by temperature than the rate of reaction. The OP would be better off making as strong as solution possible with warm to hot water then the thickening it with wallpaper past and applying it to the stains and leaving for several hours or even days before washing off.
Whilst Oxalic acid is poisonous it is by ingestion more than by adsorption through the skin, by all means take reasonable precautions wear gloves and don't drink the solution and wash your hands in cold water should you get it on your hands at some point but it is not the horror chemical often portrayed on here by some posters. It is wise to understand what it is and how it works and where it is applicable, I speak as a chemist.

 

[Fr J Hackett]

Thanks to all for very useful tips and info. I went back to the boat today and the bit I’d done on Weds actually looks pretty good now, much better then when I rather despondently gave up and left it. I’ll persevere with a stronger solution in hot water and then try bleach or Patio Magic on any remaining stubborn avian ordure stains.

Voilla see the above post #18 for a simple explanation

 

[Ribtecer]

Oxalic acid works by converting stains usually iron or similar metal based insoluble stains into soluble ones which can be easily washed away, it maybe that the bird poo and stain is largely organic and thus the oxalic acid is ineffective. Like all chemical reactions the conversion of say iron oxide to the soluble oxalate is temperature dependant, basic thermodynamics, it is also very dependant on concentration which is more effected by temperature than the rate of reaction. The OP would be better off making as strong as solution possible with warm to hot water then the thickening it with wallpaper past and applying it to the stains and leaving for several hours or even days before washing off.
Whilst Oxalic acid is poisonous it is by ingestion more than by adsorption through the skin, by all means take reasonable precautions wear gloves and don't drink the solution and wash your hands in cold water should you get it on your hands at some point but it is not the horror chemical often portrayed on here by some posters. It is wise to understand what it is and how it works and where it is applicable, I speak as a chemist.

Thank you for that, makes sense.

I've been told that a layer of oxidation builds up on the gelcoat and this needs to be stripped back by a "mopping' process to reveal fresh getcoat and this can only be done so many times. I'm hoing this is not the case with my boat.

As said above, the oxalic acid treatment worked really well on my hull, problem was the staining came back almost immediately after its re launch.

I am hope I was incorrect in re-polishing the hull, when I should have sealled it with a wax product.

I shall wait until the spring and redo the OA treatment followed by plenty of wax.

Boat is a 7m Rib that is in excellent condition other than its "dirty" looking bottom, lives in a rack during the summer, barn in the winter.