How to Remove Rust from Cast Iron

Do not throw out a rusty cast iron pan. Rust is only surface-deep - the iron beneath it is perfectly good - so almost any rusty pan can be rescued. Scrub off light rust with a chainmail pad, dissolve heavy rust in a timed vinegar soak, then re-season. A pan you find crusted orange at a yard sale can be cooking dinner by tonight.

Why a rusty pan is almost never ruined

Rust is iron oxide - the compound that forms when iron meets water and oxygen. On a cast iron pan it forms a thin, flaky layer on the surface, but the pan is a thick, solid casting. Removing the oxide simply exposes the clean iron underneath, which is why the process is fully reversible. Unless a pan has actually rusted through into a hole (nearly unheard of), there is good metal waiting under the orange.

Rust also is not poisonous. A little iron oxide is not going to hurt you. You still want it gone, though, because rust keeps spreading and no seasoning will bond over it - so we clean the pan back to bare metal, then rebuild.

Match the method to the damage

Light rust: scrub it off

For a light dusting - the kind that appears when a pan was put away damp - you rarely need anything but abrasion.

1. Run the pan under hot water and go over the rust with a chainmail pad or a ball of steel wool. Add a squirt of dish soap - since you are stripping back to metal here, soap is welcome.
2. Work every rusty spot until you see clean gray iron and the orange is gone. Rinse.
3. Dry the pan immediately and completely on a warm burner - bare iron with no seasoning will flash-rust in minutes if left wet.
4. Go straight to re-seasoning (below). Do not let a stripped pan sit overnight.

Heavy rust: the vinegar soak (and its strict timing rule)

When a pan is crusted with rust - a garage-sale rescue, say - a soak in a 1:1 mix of plain white vinegar and water dissolves the oxide chemically so you barely have to scrub. This works because the acetic acid in vinegar reacts with and dissolves iron oxide. Here is the catch, and it is the most important sentence on this page: vinegar does not stop at the rust. Left too long, the same acid attacks the good iron underneath and pits the pan permanently. Timing is everything.

1. Mix a 1:1 bath of white vinegar and water in a tub big enough to submerge the pan completely.
2. Submerge the pan and set a timer for 30 minutes. Do not walk away and forget it.
3. Check it every 30 minutes. Pull the pan out, scrub a test patch, and see if the rust wipes away. Heavy rust may take anywhere from one to a few hours; light-to-moderate rust may need only 30-60 minutes. The moment the rust lifts easily, the soak is done.
4. Never leave a pan soaking overnight. An all-night vinegar bath can eat visible pits into the casting. When in doubt, pull it early and scrub - you can always soak again.
5. Neutralize and rinse. Once the rust is off, scrub the pan with soapy water to stop the acid reaction, then rinse thoroughly. Some people add a quick rinse with a little baking soda in water to neutralize any lingering acid.
6. Dry it instantly and fully on a warm burner. A freshly stripped pan is at its most rust-prone right now, so do not let a drop of water linger.

Then re-season - immediately

A de-rusted pan is bare metal with no protection, so it must be seasoned the moment it is dry. Follow the full seasoning method: thin coat of oil, wipe almost all of it off, bake upside down at 450-500°F for an hour, cool, and repeat two or three times to build a real base. After that first rescue-and-season, the pan is just a normal cast iron pan again - cook on it and the seasoning keeps deepening. New to all of this? Our beginner's guide walks through first cooks, and the skillet roundup covers what to buy if the rusty pan turns out to be beyond saving.

How to keep rust from coming back

• Dry on heat, never in the rack. The number one cause of rust is a pan left wet. A minute on a warm burner ends the problem.
• Keep a thin oil coat on it. That film is a moisture barrier as much as a nonstick layer.
• Do not soak or dishwash. Both are rust factories - see the cleaning guide.
• Store it dry, with air. In a humid kitchen, a paper towel between stacked pans wicks away trapped moisture.