Any advice on how to clean out a lot of rust from an old cast iron kettle? Would vinegar do it, or salt, or what?
A picture or two of the kettle would be helpful. Is it an electric kettle, gas-fired, etc kettle? If the metal is thick, then soaking it in citric acid for a couple of days would make a lot of difference.
Personally, I'd go with vinegar. No need for fancy wine, cider, balsamic etc. vinegar, plain old cheap malt will do the job. It could take two or three days - perhaps even longer if the rust is heavy.
Yup, vinegar. I have a plastic bucket of vinegar for larger pieces and day or two loosens it nicely. I follow this up with a wire brush (drill type) which gets it pretty good followed by a final dunk in the vinegar and some wire wool to finish. If the item is painted quickly after it's dry, you should get a good finish.
After it’s cleaned of rust, cure it by using vegetable oil and baking it in a 220°C oven for a few hours. There’s a lot of complete nonsense online about this process and many complicated procedures, but it’s simple: 1. Make sure the cast iron is absolutely dry. 2. Using pure vegetable oil apply a very even thin coat to all parts. I use spray can olive oil, but a tablespoon of oil from a bottle, evenly applied, and not sticky, will do the trick. 3. Put in 220°C oven for a few hours. If it’s the first cure, clean, dry, and repeat. If you’re going to use the kettle for boiling water, do your first boil with a handful of cheap tea leaves to eliminate any oil taste. Cheers Tony
Wow, ask a simple question! I will start off with the vinegar but the rust is well up the inside of the kettle, it holds 10 pints but I’ll give it a go. I certainly don’t intend using it @Tony Press.
That's an interesting 'recipe' Tony, I'll definitely try that next time I need to season some cast iron or steel. ...and Jean, we'd love to see a photo.
@ColinG In our kitchen we use cast iron every day, in many varieties, and have no issues with rusting. After use, wash without soap or detergent, light spray with olive oil, wipe, and you’re ready to go again. Cheers Tony
For a big kettle like that I'd set up a simple electrolysis rig. Some water, couple tablespoons of baking soda and a 12v 1a power supply. Hang a sacrificial anode in the center and let it rip. I've used old wall warts as power supplies or laptop power bricks. A small tin can, a piece of sheet metal a couple inches square or anything similar would make a good anode. Good luck.
Citric acid. 1Table spoon per i pint of water. Pour in, leave. It will convert the red oxide to black. Wash well use.
The kettle is now sitting with 5L of vinegar in it. Luckily I had just bought a new supply. I’ll pour it out and see what’s what after another day and will post a pic then. @Reese Williams that’s all double Dutch to me, remember you’re advising someone who is thick as the rust in said kettle.
Vinegar is still a weaker acid than citric. Therefore, it might take a tad bit longer to work through heavy rust.
Yes, Jean. Also, it is found in “home brew” shops if there’s one nearby you. For something like that, I would mix 1 teaspoon per litre; or stronger for quicker work. But your vinegar without dilution will also be a strong acid, if a bit stinky. Tony
Jean, I would persist with the vinegar. That much rust could take several weeks to remove. Be patient
Ha ha @ROBBO55 I’m certainly not known for my patience but will pour the vinegar back in then ignore it for a week or two.
For that amount of rust I'd certainly go with electrolysis. Here are a couple good demos. The first is quick and dirty, the second give a more in depth explanation of the process. In your case you don't need a container, your kettle will be the container. Suspend the sacrificial anode in the center of the kettle so it doesn't touch the kettle, pour in some water and baking soda (couple tablespoons of soda) and connect your power supply. Any power supply that has an output of 12v 1a should work, although with a heavy kettle you might need a little more power. If you use something like a laptop power supply you can just add a second one if you need more power. Do a search on this site and on the sister site Classic Camp Stoves for electrolysis. Plenty of discussions to be found. With electrolysis you can't overdo it. Plug it in an let it go. If the water gets too dirty just change it out and go some more.
Now you’re scaring me @Reese Williams, thought electrolysis was for removing unwanted hair on my chin!
Boiling it with citric acid solution would speed things up ! I buy mine in powder form on Ebay - I buy food grade but you could get cheaper
I have used electrolysis and it works great, I used an old transformer type car battery charger, you could use an old laptop power supply as well. My electrolyte was bicarb of soda and water. That kettle would probably take over night for starters.
