How to get rust off cast iron

How to remove rust from cast iron

1. 1

   Scour off the rust

   Scrub the rusty areas with steel wool or a stiff brush until the orange is gone and you see dull gray iron. Work over the sink and include the handle, rim and underside.

   Why: Rust is iron oxide sitting on and in the surface. It has to come off physically before new seasoning can bond to the iron. Steel wool is fine here, but only for rust removal, since it strips seasoning.

2. 2

   For heavy rust, soak briefly in vinegar

   If scrubbing alone doesn't remove it, soak the rusted area in white vinegar for no more than 15 minutes at a time, then scrub again. Repeat in short rounds if needed.

   Why: Vinegar's acid helps dissolve rust, but acid also attacks iron and seasoning. Mississippi State Extension limits each soak to 15 minutes for that reason.

3. 3

   Wash with warm water and a little soap

   Wash the whole pan with warm water and a small amount of mild dish soap, then rinse well. Don't soak it.

   Why: This removes rust particles, steel wool fibers and vinegar. A little soap is fine for a pan you're about to re-season.

4. 4

   Dry it completely, right away

   Towel-dry the pan, then set it on a burner on low for a few minutes until every bit of moisture is gone.

   Why: Freshly scoured bare iron rusts again within hours if any water is left on it.

5. 5

   Oil it thinly all over

   Rub a thin coat of neutral cooking oil or shortening over the entire pan, inside and out, then wipe off the excess with a clean towel until it looks almost dry.

   Why: A thin layer polymerizes into hard seasoning. Too much oil leaves a sticky, uneven coat.

6. 6

   Bake to re-season

   Place the pan upside down in the oven at about 450 to 500°F for an hour, with foil on a lower rack to catch drips. Let it cool in the oven. For a badly rusted pan, repeat 3 to 5 times.

   Why: High heat bonds the oil to the iron as a hard, slick coating that keeps water away from the metal.

Why cast iron rusts

Bare cast iron rusts readily in moisture. What protects it is seasoning: thin layers of oil baked on at high heat until they polymerize into a hard coating. When seasoning wears thin, from soaking, the dishwasher, scouring or acidic foods, water reaches the iron and forms rust, iron oxide.

That's why rust on cast iron is a mineral stain you remove mechanically, and why the job isn't finished until the pan is re-seasoned. On fabric and carpet, rust is treated very differently, with acids that dissolve it; that's covered on the rust stain page.

Soap, vinegar and steel wool: where the advice differs

A cast iron manufacturer and the Maine and Illinois extension services say a small amount of mild dish soap is fine on cast iron. Mississippi State Extension advises no soap. Before re-seasoning, a little soap does no harm, because you're rebuilding the coating anyway.

Steel wool is a rust tool only: extension guidance warns it strips seasoning in routine cleaning. Vinegar works on rust but breaks down seasoning, so keep soaks short. Everyday care is in how to clean cast iron.

By situation

A few small rust spots

Scrub just those spots with steel wool, wash, dry on the stove, oil lightly and heat the pan on the burner for a few minutes, or do one round in the oven. Small patches don't usually need multiple coats.

A pan covered in rust

Use short vinegar soaks and thorough scouring until it's all bare gray iron, then re-season 3 to 5 times to build a new coating. Heavily pitted heirloom pans can also be professionally restored.

Rust after the dishwasher or soaking

Both strip seasoning. Scour the rust, then re-season the whole pan, since the coating is likely thin everywhere.

Rust on enameled cast iron

Enameled cast iron has a glass coating instead of seasoning, so rust shows up only where iron is exposed, such as an unglazed rim. Follow the maker's care directions and don't use steel wool on the enamel.

Sticky or dull patches, not rust

Sticky spots are oil buildup and dull ones are worn seasoning. Neither needs steel wool. Scrub with salt and a little water, then oil and heat.

What not to do

• Don't soak cast iron in water or run it through the dishwasher. Prolonged water contact causes rust, and the dishwasher removes seasoning.
• Don't leave it in vinegar longer than 15 minutes at a time. Acid breaks down seasoning and attacks the iron itself.
• Don't air-dry it or store it damp. Bare iron oxidizes quickly when wet.
• Don't use steel wool for routine cleaning. It strips seasoning. Reserve it for removing rust.

Other methods that work

Coarse salt scrub

For light surface rust or stuck food, a paste of coarse kosher salt and a little water scrubbed with a cloth or brush is gentler than steel wool.

Caution: It's for light rust only. Dry and oil the pan afterward.

Professional restoration

Heavily rusted or pitted heirloom pieces can be professionally restored.

Caution: Cracked or warped pans can't be repaired at home or by restoration.

Stain still there?

Rust came back a day after cleaning

The pan wasn't fully dried or oiled. Scour the spot, dry it on the burner, oil it thinly and bake again.

The new seasoning is sticky

Too much oil was applied. Wipe it thinner next time, and bake the pan again for an hour to finish curing the sticky layer.

The surface looks patchy or gray after one round

The new coating is still thin. Repeat the oil-and-bake round; the University of Maine suggests 3 to 5 rounds to build a new coating.

Safety

• Use oven mitts: the pan stays hot for a long time after re-seasoning.
• Ventilate the kitchen while seasoning, since oil smokes at high heat.

Never mix cleaning products; see chemicals you must never combine.

Questions

Rust on other surfaces

• Rust stains: the complete guide
• Rust on carpet
• Rust on clothes

Other stains on cast iron

• How to clean cast iron