Does Cast Iron Rust?

Cast iron is a widely used metal throughout the world. There are many types including grey cast iron, white cast iron, ductile cast iron, and malleable cast iron. Although these all have distinct properties, they are all strong and reliable metals used in a range of ways.

Cast iron is not a relatively newfound metal. The earliest cast-iron artifacts date back to the 5th century in China. That leaves the question: if cast iron lasts that long, can it rust? Well, yes, cast iron can indeed rust.

Cast iron tends to be brittle with the exception of the malleable type. It has a relatively low melting point with good fluidity. Along with having castability and wear-resistant properties, cast iron has become a popular engineering material for many applications. These include pipes, automobile parts, and machinery components. Cast iron is also resistant to damage caused by oxidation. But this doesn’t mean it can not rust.

The speed that cast iron rusts is relative to the environment it is in. Good quality cast iron that is thick will not rust very quickly. However, rust is permeable so it can actually protect the surface below it over time. Oxygen needs to reach the lower layers of cast iron to make iron oxide but it requires a surface area to do so. 

On the other hand, lower-quality cast iron can rust before your eyes. Take cast iron brakes and rotors for instance. These can develop a fine layer of dust in just a few minutes when left in extremely humid conditions.

Cast iron that is most susceptible to rust is that used in cookware. This is made from a mixture of pig iron, steel, and alloys. When there is no protective layer of carbonized oil, known as seasoning, cast iron becomes susceptible to rust. Leave your cast iron pan in the sink to soak too long or store it in a moist area, then it will eventually rust. 

However, this build-up of rust on cookware is generally pretty easy to clean so don’t go throwing all of your pots and pans out just yet.

Is rust on cast iron dangerous?

Most cast iron pans become rusty after some time. Even the best quality cookware that you have meticulously taken care of over the years will eventually become susceptible to rust. When many of us see this rust, we automatically worry that our cookware is beyond repair and the rust is too dangerous to cook with anymore. But is this true?

Rust is nothing but oxidized iron. It is not dangerous to humans unless your body cannot remove iron effectively. Of course, if you digest large amounts of rust, it can become extremely dangerous and life-threatening. But small amounts on your favorite kitchen pans shouldn’t be a cause for concern.

That being said, you should still remove the rust from the cast iron to be on the safe side. Most culinary experts believe that rusty cast iron is entirely salvageable. Experts at the University of Illinois at Urbana-Champaign concluded that a little amount of rust on cast iron cookware was unlikely to harm you in any way. The same goes for a little rust in drinking water. 

Rust is simply iron oxide. In small quantities, it is a rather benign substance that is unlikely to cause any health hazards. Too much iron in a person’s diet can become problematic but if you’ve just found your old tongs and found rust on them, you should be safe to use them. 

While rust isn’t dangerous, if it is left on your cookware, there is a higher risk of it getting transferred to your food when you cook. This may not make your meal dangerous but it can result in terrible tasting food. Rust can also hold other forms of bacteria, especially on the bottom of cast iron pans. The rust may be harmless but the build-up of bacteria could cause some health concerns. Therefore, you should clean the rust off.

Does coke remove rust from cast iron?

If you’re looking for an inexpensive way to remove rust from cast iron, then coca-cola is the way to go. The chemicals in this soda help loosen the rust and, in turn, make it much easier to scrub off afterward without the need for any harsh cleaners.

Cast iron appliances and tools can last for decades. However, they are still prone to rust as they grow older and if they come into contact with moisture. To deal with a rusted piece of cast iron, the answer could be in your refrigerator. 

Coca-cola contains phosphoric acid. This is a chemical used in commercial rust removers that work on breaking down rust. 

Removing rust with coke is simple. All you have to do is fill your sink or a bucket with coca-cola before submerging the cast iron object inside. Let it sit overnight to allow the soda to loosen the rust. The next day, grab a wire brush and scrub off the loosened rust from the cast iron surface.

If you want to remove smaller spots of rust, just soak the affected area of cast iron in coke for an hour or so and then scrub off with a sponge.

Once you have cleaned away the pesky rust, you will need to rinse, dry, and season the cast iron. This will prevent the iron from oxidizing again and forming additional rust.

When we say season, we don’t mean to sprinkle some ginger on top. To season effectively:

  • Heat the cast iron in the oven at 350 degrees
  • Wait until the cast iron is hot
  • Take it out and rub it down with a canola oil-soaked paper towel
  • Next, heat the freshly seasoned cast iron object upside down in the oven at 500 degrees
  • Wait until it stops smoking
  • Carefully take out and wait for the cast iron to cool down

The cast iron should now be ready to fight another day!

Does vinegar remove rust from cast iron?

We all know that our cast iron cookware is reliable and dependable. But we also know that it requires a little more tender loving care than the ordinary pan.

As we now understand, cast iron rusts. There is no getting away from this. But, as well as coca-cola, there are other methods when trying to remove rust from cast iron. One way is through the use of vinegar.

The process of removing rust with vinegar is pretty straightforward. Here’s how:

  1. Measure out equal parts of white vinegar and water - Vinegar won’t clean the rust alone. Therefore, you must measure out an equal 50/50 ratio of water and vinegar. This should be enough to submerge your cast iron item. Mix in a sink or separate bucket or pan.
  2. Submerge and soak the rusted cast iron - Place the affected cast iron into the vinegar and water mixture until it is completely submerged. Leave to soak for up to 8 hours. However, you should check the cast iron every half hour to see if any rust has already come off. If you see the rust has been removed, simply take the cast iron object out of the rust removal solution.
  3. Remove the cast iron from the solution and scrub - Once you have taken the cast iron out of the vinegar and water mixture, you need to wash it right away. Do this by using a soft scrub or brush. Gently scrub to remove any rust residue. Make sure you don’t scrub too hard as you may damage the surface. Then, dry down the iron with a paper towel.
  4. Place the cast iron in the oven - Once dried, place the cast iron into your oven for 30 minutes at a high heat (350 degrees or more).
  5. Season the cast iron - Once heated up, remove the cast iron and re-season it with either canola oil, vegetable oil, or olive oil.
  6. Reheat in the oven - Heat at around 450 degrees with the cast iron upside down. Wait for an hour or two and remove. 
  7. Cool and store - Make sure you leave it cool down and then store it in a dry place.

How do you clean rust from cast iron?

Cast iron is so useful because it seems to last forever. Even when it’s rusty, you can restore it in several ways. As well as using coca-cola and a water/vinegar solution, you can take advantage of some other methods to restore your cast iron skillet to its former glory.

You can remove minor traces of rust with some oil and heat. Afterward, just gently rub the flakes off with a paper towel and keep the cast iron dry. 

Here is a list of ways to remove unwanted rust from your cast iron items:

  • Use dish soap
  • Use sea salt and a potato scrubbing combination
  • Heat in a self-cleaning oven for heavy-duty rust removal

Of course, the best way to keep your cast iron rust-free is to keep it dry and away from any humid, moist areas. This is the number one tip for keeping your cast iron rustless for longer. Along with regular seasoning, you shouldn’t have to resort to rust removal for a long time yet.