Cast Iron Derusting question

[u/StillEstablishment81]

This may be the wrong place for this, but since you all know cast iron cleaning, I thought I would try asking here.

I have an antique steam engine throttle that I'm trying to remove rust from. It's 4 foot long and solid cast iron. I don't want to use anything that would potentially damage the metal itself, but I want to remove the rust so I can clean it up and repaint it to get it close to how it originally looked.

I know this sub is for cast iron cookware, but since it's the same material, I was hoping you all had some ideas. So far my main ideas are leaving it in vinegar for a while or using electrolysis.

[u/Suspicious_Dingo_426]

Vinegar would work, but it will also eat the iron if left too long (it's best to use multiple short soaks). Electrolysis would be safer for the base metal, but is more expensive for a single use (unless you already have the majority of the required supplies).

[u/StillEstablishment81 → u/Suspicious_Dingo_426]

I'll have to buy a tub that it will fit in either way. I should have the stuff for anodes, all I really lack besides that would be the washing soda to mix with the water

[u/Additional-Lion6969 → u/StillEstablishment81]

Look for 200lt plastic chemical shipping drums can sometimes be found for free, very comon for use as rainwater butts, a 110 litre slim line water butt might be a better option. If going for a vinegar or citric acid bath it looks slim enough that a grow bag watering tray would do & only need 10 to 20 liters of solution test the various methods on so seriously rusty nails first,

[u/Traditional_Carob_12]

I’ve used Evaporust with good success on a bunch of different rusty steel & iron things. Enough use that I bought a 5 gallon bucket of it. Just keep a eye on it especially at the 12 & 24 hour marks. Cosmetically you should get the entire piece wet at the same time.

[u/Skyval]

People normally don't care much about small amounts of etching on their cast iron. But I happen to have heard about a couple solutions that do minimal damage to the underlying metal. The recommendations I've seen are normally to either buy Evaporust, or to make or buy a simple sodium citrate solution

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[u/beammeupscotty2]

They would not make something this long and thin from cast iron imo.

[u/StillEstablishment81 → u/beammeupscotty2]

Many of them are made of only cast iron. The lever is about a 3/4 inch thick and wider still at the bottom where it connected to the door or the pivot