oxalic acid

[whiteoaks7]

Last year my neighbour in Preveza passed on some left-over oxalic acid mix he'd used to clean the rust off his brightwork. It was, he said, oxalic acid mixed with wallpaper paste and we could paint it on the stainless bits then wash it off a short time later and off came the rust with it. Being half asleep at the time I neglected to ask for the recipe. Anyone out there have a favourite mix for a nice sticky rust cleaner?

 

[puddock]

Oxalic Acid, Water & thicken with wallpaper paste mix.........

 

[pappaecho]

Dont eat it,,, it is highly poisonous, use gloves at all times!

 

[longjohnsilver]

Oxalic Acid, Water & thicken with wallpaper paste mix.........

Yes but don't leave it to set, it then takes an age to get off, particularly when you've plastered it all over a 50' hull............

However it does work a treat, took all the stains off the hull and cost pence to do.

 

[Rigger Mortice]

Yes but don't leave it to set, it then takes an age to get off, particularly when you've plastered it all over a 50' hull.............

Yup. Been there. Done that.

 

[Humblebee]

Readily available on ebay, works well as teak cleaner too.

 

[MM5AHO]

I mix mine with fairy liquid.
I have a 500ml plastic container. Add two tablespoons of oxalic acid powder, add enough hot water to dissolve, but leave some room for the detergent. Add about 50ml green fairly liquid, and stir gently.

When applying I use a washing up bush and brush vigorously to get a lather. The lather keeps it moist long enough to do the job, and the detergent removes a few things the acid won't. The bubbles also show where I've been and where not yet.

Cheap and effective.

 

[charles_reed]

Dont eat it,,, it is highly poisonous, use gloves at all times!

Hardly:-

In humans, oxalic acid has an oral LDLo (lowest published lethal dose) of 600 mg/kg.

Slightly toxic, might be more appropriate.

As to wearing gloves - it's more likely to roughen the skin, in saturated solution, than to kill.

 

[ianabc]

US limits

NIOSH (REL) Recommended Exposure Limit, 1 mg/m3 TWA, 2 mg/m3 STEL

Health Factors

Corrosive to tissue... When ingested, causing sore throat, burning sensation, abdominal pain, vomiting, diarrhoea, passing stools with blood, drowsiness, loss of feeling in fingers and toes. Oxalic acid removes calcium from the blood causing kidney damage as the calcium is removed from the blood in the form of calcium oxalate. The calcium oxalate then obstructs the kidney tubules.

Harmful if inhaled... Can cause severe irritation and burns to nose, throat, and respiratory tract. Irritations of mucous membranes, eye discomfort and burns, blue colouration of lips, fingernails or skin, shock, collapse, convulsions, kidney damage, pulmonary oedema.

Toxic... May cause burns, nausea, gastroenteritis, vomiting, shock and convulsions. May cause renal damage, as evidenced by blood in urine. Estimated fatal dose for humans is 5 to 15 grams.

Skin Contact... Can cause severe irritation and skin burns. May be absorbed through the skin.

Eye Contact... Oxalic acid is an extreme eye irritant by virtue of being corrosive and physically abrasive.

Chronic Exposure... Causes inflammation of the upper respiratory tract. Prolonged skin contact can cause dermatitis, cyanosis of the fingers and ulceration. May cause kidney damage.

Pre-existing Conditions... Exacerbates pre-existing skin disorders or eye problems, kidney problems or respiratory complaints.


http://www.dave-cushman.net/bee/oxalicproperties.html

 

[rafiki_]

NIOSH (REL) Recommended Exposure Limit, 1 mg/m3 TWA, 2 mg/m3 STEL

Health Factors

Corrosive to tissue... When ingested, causing sore throat, burning sensation, abdominal pain, vomiting, diarrhoea, passing stools with blood, drowsiness, loss of feeling in fingers and toes. Oxalic acid removes calcium from the blood causing kidney damage as the calcium is removed from the blood in the form of calcium oxalate. The calcium oxalate then obstructs the kidney tubules.

Harmful if inhaled... Can cause severe irritation and burns to nose, throat, and respiratory tract. Irritations of mucous membranes, eye discomfort and burns, blue colouration of lips, fingernails or skin, shock, collapse, convulsions, kidney damage, pulmonary oedema.

Toxic... May cause burns, nausea, gastroenteritis, vomiting, shock and convulsions. May cause renal damage, as evidenced by blood in urine. Estimated fatal dose for humans is 5 to 15 grams.

Skin Contact... Can cause severe irritation and skin burns. May be absorbed through the skin.

Eye Contact... Oxalic acid is an extreme eye irritant by virtue of being corrosive and physically abrasive.

Chronic Exposure... Causes inflammation of the upper respiratory tract. Prolonged skin contact can cause dermatitis, cyanosis of the fingers and ulceration. May cause kidney damage.

Pre-existing Conditions... Exacerbates pre-existing skin disorders or eye problems, kidney problems or respiratory complaints.


http://www.dave-cushman.net/bee/oxalicproperties.html

Very helpful, but oxalic acid is best prescribed for a boat.

 

[Deleted member 36384]

..... Anyone out there have a favourite mix for a nice sticky rust cleaner?

I read on here that you keep adding the graduals to, say a 1/2 litre of cold water, until no more dissolve. This solution, which is at the saturation level, is then mixed with wall paper paste until thickened.

 

[bigwow]

And don't leave some in a bucket with a snap-on scraper in, as it ate half the blade!

 

[Hoolie]

I mix mine with fairy liquid.
... ... ...

Cheap and effective.

Agreed. Leave out the wallpaper paste, it's messy and poisonous as well!
In my experience the acid acts pretty well immediately and there's no need to leave it on for long. Concentration doesn't really matter either because as it dries it gets stronger.

 

[rogerthebodger]

Take a note of what bigwow says about as to eating the blade of a snap on scraper.

Oxalic acid will make your stainless steel go dull after several applications.

It gets rid of the rust by dissolving the iron oxide which will leave the surface ruff and thus shine.

The only way to restore the shine is with mechanical polishing.

 

[macd]

Last year my neighbour in Preveza passed on some left-over oxalic acid mix...

Think that was maybe me, Whiteoaks. Were you near the top of the yard by the fence?
My practice (I'm no chemist) is to dissolve crystals in warm water until no more will dissolve. Allow to cool, then add wallpaper paste. As you may remember, wallpaper paste takes a while to thicken, so add it conservatively or the mix becomes too thick. You can always add more.
Cautions about washing off before it hardens in the sun are well made.

 

[Bodach na mara]

I have not found that adding the paste granules caused any thickening at all.

I started by mixing up the strong oxalic solution, added a few drops of Fairy liquid then gradually added what would have been the amount of paste granules for a thin gloopy paste. The result was still as runny as water. I added the same amount of paste again, then twice as much again. By this time the paste granules were failing to disolve and lying at the bottom but the stuff at the top was still runny!

I

 

[Scotty_Tradewind]

I bought a small tub from these people..... http://www.agwoodcare.co.uk/prod/oxalic_acid.html

All the instructions/guide etc on their website.... http://www.agwoodcare.co.uk/more_info_oxalic.html

Good service/quick delivery.

 

[nigelmercier]

Anyone out there have a favourite mix for a nice sticky rust cleaner?

You need a 10% solution: 100g in a litre of warm water. Add paste if required, I've never bothered.

Inspect after 15 minutes, leave longer if needed.

 

[ghostlymoron]

I mix mine with fairy liquid.
I have a 500ml plastic container. Add two tablespoons of oxalic acid powder, add enough hot water to dissolve, but leave some room for the detergent. Add about 50ml green fairly liquid, and stir gently.

When applying I use a washing up bush and brush vigorously to get a lather. The lather keeps it moist long enough to do the job, and the detergent removes a few things the acid won't. The bubbles also show where I've been and where not yet.

Cheap and effective.

Very good response and includes the recipe which is what the bloke wanted!

 

[Ian_Edwards]

Is there a minimum temperature, below which oxalic acid isn’t effective, I seem to remember reading somewhere that below 10 deg C it doesn’t really work that well.
Anyone out there know if that is true? It’s only 7 deg C up here in Aberdeen at the moment.