Cast Iron Pans: Rust, Reasons And Remedies

Cast iron pans are beloved by many home cooks, but they can be a little high-maintenance. One of the most common issues is rusting, which can happen if the pan is left to soak, put in the dishwasher, air-dried, or stored in a moisture-prone environment. Luckily, it's possible to restore a rusty cast-iron pan to its former glory. The first step is to remove the rust, which can be done with steel wool, a scouring pad, or even a vinegar soak for more serious cases. After removing the rust, the pan should be washed, dried, and coated with a thin layer of oil before being placed in the oven to season. With proper care and maintenance, a cast-iron pan can last a lifetime.

Cast iron reacts with oxygen and water

The formation of rust on cast iron can be prevented by creating a protective layer on the iron through a process called seasoning. This involves coating the cast iron with a thin layer of seasoning oil, which not only creates a non-stick surface but also protects the iron from reacting with oxygen and water.

If rust does occur on cast iron, it can be removed by scrubbing with steel wool or a scouring pad, washing with mild dish soap, and thoroughly drying the item. The cast iron can then be reseasoned by coating it with a thin layer of cooking oil and baking it in the oven at a high temperature.

Leaving water on cast iron for too long

To prevent rust, cast iron should be dried promptly and thoroughly with a lint-free cloth or paper towel after washing. It is recommended to dry the pan over medium-low heat on the stove to evaporate any lingering water that might not be clearly visible to the naked eye. Once the skillet has been washed and thoroughly dried, it should be coated all over with a thin layer of seasoning oil (both on the inside and the outside of the pan). This will protect the pan from rusting while it is not in use.

If rust does develop on a cast iron pan, it can be removed by scrubbing the rusty sections with steel wool or a scouring pad and then washing the pan with warm, soapy water. The pan should then be completely dried and coated with a thin layer of cooking oil before being placed in the oven upside down at a high temperature for an hour to restore the seasoning.

Properly drying cast iron after use

To dry cast iron properly after use, it is recommended to follow these steps:

Firstly, gently wash out the skillet with hot water and a bit of soap. You can use a brush to clean the skillet thoroughly without being too abrasive and potentially taking off the seasoning. Then, wipe out most of the water with a towel or paper towel.

Secondly, place the skillet over a medium flame and let it sit until very dry—approximately 5 minutes. This ensures that any lingering water that might not be visible to the naked eye is evaporated. Cast iron is porous, so there may be some moisture remaining even after drying the pan with a towel.

Finally, let the skillet cool down, give it one last wipe, and then put it away. This technique not only effectively dries the cast iron but also helps preserve and maintain the seasoning.

The protective layer of carbonized oil

Cast iron pans are made of a mix of pig iron, steel, and alloys. Without a protective layer of carbonized oil, also known as seasoning, cast iron pans are susceptible to rust. This is because the iron in the pan reacts with oxygen and water to form rust (iron oxide).

Seasoning is a layer of carbonized oil that has been baked onto the pan, forming a protective layer. This protective layer gives the pan a natural, easy-release finish and makes cleaning easier. The protective layer is created through a process called polymerization, where oils or fats are heated at a high enough temperature to change from a wet liquid into a slick, hardened surface. This reaction creates a layer of seasoning that is molecularly bonded to the iron.

The more you cook in a cast-iron pan, the thicker the layer of oil becomes, transforming the pan into an heirloom with a smoother and darker cooking surface. Each time you cook with oil or fat, you add another layer of seasoning to the pan. Over time, these layers build up to form a strong, non-stick cooking surface.

To create this protective layer, you can follow these steps:

• Wash the pan with warm, soapy water.
• Dry the pan thoroughly with a paper towel or lint-free cloth. You can place it on the stovetop on low heat to ensure it is completely dry.
• Add a very thin layer of cooking oil to the entire surface of the pan, inside and out. Be sure to use just a thin layer to avoid dripping or running.
• Preheat your oven to between 350 and 500 degrees Fahrenheit. Place aluminum foil on the bottom rack to catch any excess oil.
• Place the pan upside down on the center rack of the oven. This helps prevent oil from pooling on the cooking surface.
• Bake for 1 hour, then turn off the heat and allow the pan to cool in the oven. This allows the seasoning to further cure and adhere to the iron.

Removing rust with a vinegar soak

Cast iron skillets are great for cooking, but they require more maintenance than your average pan. Cast iron is prone to rusting, and this happens when iron reacts with oxygen and water. If you leave water on your cast iron pan for too long, it will start to rust. This can happen if you leave it to soak, put it in the dishwasher, or let it air dry.

If your cast iron skillet has rust, don't panic. You can restore it to its former glory with a few simple steps. For minor surface rust, you can use a scouring pad or kitchen towel to rub kosher salt into the surface of the pan until the spots of rust are removed. For more serious cases, you can use a vinegar soak. Here's how to do it:

• Mix equal parts water and distilled white vinegar in a container that will fit your cast-iron skillet, such as a bucket or a deep pan. Make sure the container is big enough to submerge the entire pan, including the handle.
• Submerge the cast-iron skillet in the vinegar solution. Check the pan every 15 minutes or so. The vinegar will dissolve the rust. The process can take anywhere from one to eight hours, so frequent check-ins are important to ensure the skillet doesn't soak for longer than necessary.
• Once the rust easily flakes away or has been loosened, remove the pan from the solution. Be careful not to leave the pan in the vinegar solution for too long after the rust has been removed, as the vinegar can start to eat away at the cast iron itself.
• Wash the pan with mild dish soap and warm water to remove any remaining vinegar residue. Use a mildly abrasive sponge or scrub brush to clean away any lingering rust.
• Dry the pan immediately and thoroughly with a kitchen or paper towel. You can also place the pan on the stovetop over low heat for a few minutes to ensure it is completely dry.
• Re-season the cast iron. Apply a thin layer of neutral cooking oil with a high smoke point, such as vegetable oil, all over the pan, inside and out. Then, buff any excess oil and place the pan upside down in the oven at 350-500°F for about an hour. Turn off the heat and let the pan cool in the oven.

After removing the rust and re-seasoning your cast iron skillet, it's important to properly clean and store it to prevent rust from forming again. Always dry your pan completely after washing and store it in a dry, low-humidity area.

Frequently asked questions