[yankieGirl]

I inherited a rusty old cast iron cauldron that has been used as a flower planter for years.  I would like to use it (for a chicken scalder for now) but need advise on how to remove the rust.

Can I build a fire in it and burn the rust out?

Any advise is appreciated.

[Plantoid]

Kettle descaler such as citric acid in hot water filled to the top and heated up or filled with boiling water will  remove lots of rust once you have wire brushed out most of the bigger stuff after the cauldren has had a few days drying time.

 Once it's de rusted it will rust again so rub some cooking oil  on a cloth around the inside of  it when it is hand hot & dry

 don't heat it on the cooker till you have prooved that the cleaned cauldren  has no leaks in it when filled with almost boiling water  old rusted cast iron cauldrens that have been earth filled have a tendancy to leak ... that's why they get used as planters in the first place.

[MAK]

Yes check for leaks!
I spent an age and too much energy clearing our hangar ,dragging an old wood burning cooker into it then raising it up on bricks. I fitted the metal flu out and up the outside of the hangar and carefully added an extension length of "chimney". My son and I moved a tree stump that we towed then rolled next to the cooker (it is over waist height and big enough to dress large ducks on) The plan was to use the tree stump as a work surface next to the stove. I cleaned the oven and the hot plates then firred up the cooker. Having cleaned the cauldron ( found in our barn)  I filled it and lifted it on the hot plate.Sodding cauldron leaked - steam everywhere !
I now use the oven to store root veg that I then cut up and cook in a smaller pot on a gas ring on top of the tree stump!!!!
Always check a pot before you ----- in it.
Martin

[robert waddell]

sand blasting or bead blasting can bring it back to bright metal after you have done the inside you will see if there are severe pitting   hold it up to the sun you will see the obvious holes or get a torch and shine it in the cauldron                      if you know an engineering firm that recovers engine blocks  ask them to de scale it in the fertone tank

[yankieGirl]

what is citric acid (I know lemon juice etc).  I mean in a form I can use for such a large kettle?

I know it doesnt leak (nothing major) bc it has been sitting out for a year and we have to keep dumping the rain water out of it.

Thanks to all.

[Plantoid]

Our citric acid crystals are a standard commercially available hardware shop product that we used to use for taking the lime scale out of electric kettles when we lived in a high lime content water area ( also known as hard water ) they were cheap at around £1.20 per packet of five sachets .
 There are also formic acid based descalers but  I don't know how effective they would be on rust .

[deepinthewoods]

it may not leak when its full of cold water, but it may well when full of boiling water!

[chrismahon]

If you heat old cast iron locally it will most probably crack. Only suitable for slow warming, as when it is full of water. Robert Waddell's idea for bead or sand blasting is good. This is the treatment for restoring the old cast iron radiators. Then you test for leaks.