Pickling copper with Citric acid

[outofthefire]

For my latest sculpture i'm making butterflies from old copper pipe then brazing them together, there will be 100 - 150 all together. They've got years of oxidization and limescale on them plus the fire scale and flux from the brazing will citric acid clean them back to bright. I read somewhere that copper pans used to cleaned with lemon dipped in salt, would it be more effective if I added salt to the acid. I know other acids and vinegar can be used but I have decent sized vat of citric acid that I use for rust removal.

 

[123hotchef]

copper pans needed rubbing with the salt and lemon juice not sure a soak would clean them up

 

[hotrodder]

As above i don't think just soaking will do much but it's not gonna cost much to find out...
I've got a vague recollection that rhubarb (oxalic acid) leaves is/was the tradtitional method for copper and it's alloys?

 

[outofthefire]

As above i don't think just soaking will do much but it's not gonna cost much to find out...
I've got a vague recollection that rhubarb (oxalic acid) leaves is/was the tradtitional method for copper and it's alloys?

That's typical, i've a huge rhubarb plant at the side of the pond that's just died back for winter.

 

[outofthefire]

I've seen a recipe using white vinegar, salt and hydrogen peroxide but you're supposed to heat it for it to be useful and i've nothing big enough for that. I've also read you can use muriatic or sulfuric acid but i'd need a fair bit and i'm not really comfortable using it in that quantity.

 

[123hotchef]

how hot do u need to heat it too

 

[hotrodder]

That's typical, i've a huge rhubarb plant at the side of the pond that's just died back for winter.

Instead of waiting 'till spring oxalic acid powder/crystals are almost as cheap and easy to buy as citric. Whether soaking would be enough i don't know but oxalic can be used to clean other stuff too and is (the main one at least) the active ingredient in bars keepers friend IIRC

 

[outofthefire]

how hot do u need to heat it too

The couple of videos I've seen they use a slow cooker so I'm guessing close to boiling, they also day it's next to useless cold, which is probably the same for citric acid.

 

[outofthefire]

Instead of waiting 'till spring oxalic acid powder/crystals are almost as cheap and easy to buy as citric. Whether soaking would be enough i don't know but oxalic can be used to clean other stuff too and is (the main one at least) the active ingredient in bars keepers friend IIRC

Do you know where I can buy it?

 

[hotrodder]

The bay is probably the easiest and cheapest?

 

[eSCHEn]

Do you know where I can buy it?

Here you go honey buns http://darrantchemicals.co.uk/oxalic-acid

 

[chunkolini]

Try your citric acid vat first.
I use it for descaling my coffee machine and kettle; very effective.

 

[Mee]

Coca Cola works just as well as anything commercial on the market, so if it does this to copper then imagine what it does to your guts.