So, why does cast iron rust? What is cast iron itself? Cast iron cookware is prized for its heat retention, durability, ability to withstand extremely high temperatures, and nonstick properties when properly seasoned. It can also withstand extreme conditions such as a fire or boiling water.
Cast iron cookware has been in use since ancient times; it was first introduced by Chinese potters around 1000 CE. In modern usage the term “cast iron” refers to all types of carbon steel with an approximate composition of 2%–4% chromium, 0.5%–2.0% nickel, and 1.0%–1.8% manganese, depending on alloying elements added. Other common impurities include aluminium and silicon. In this blog, we have an article about staub cast iron review that you might want to see about it.
Always among the gold standards for kitchen equipment, cast-iron cookware is enjoying a surge in popularity.”Heather MacMullin, author from chatelaine.com
Why Does Cast Iron Rust
So, why does cast iron rust? The primary reason why cast iron is susceptible to corrosion is because of the presence of iron oxide . The iron core of cast iron is covered by a porous surface layer composed mostly of iron carbides and/or iron oxides. These layers are formed during casting. Over time these layers tend to separate from each other and peel away, exposing more metal underneath which then starts to corrode.
This corrosion reaction produces acids that attack the surrounding materials and cause deterioration. To prevent this, some manufacturers add phosphate coatings, zinc, tin and other metals to the surface. However, even if the coating is effective, there may still be corrosion between individual pieces of ferrous material. There are several ways to stop the process of corrosion:
- Powder Coating – A powder coating consists of particles of non-corrosive metals suspended in waxes. When heated, the wax melts and flows over the ferrous substrate, forming a smooth protective layer over the rusty area. Powder coated surfaces do not require any additional treatment after application.
- Titanium Dioxide – Titanium dioxide is applied to cast iron dishes to reduce the rate of oxidation.
- Phosphate Coatings – Phosphate coatings are durable anti-wear coatings applied to cast irons. They increase the life span of cast iron utensils by preventing corrosion. There are three different kinds of phosphates – red, yellow and blue . Red phosphates provide maximum protection against acidic foods like tomato sauce, while blue phosphates protect against alkaline foodstuffs such as eggs.
- Waterproof Coatings – Some producers make cast iron objects that have a waterproof coating on them.
- Copper Plated – Copper plated cast iron is resistant to corrosion from acid foods due to copper’s positive effect on pH.
- Aluminum Foil – Aluminum foil can be wrapped around a cast iron pan to create a barrier to moisture and retard the corrosion process.
Cast iron. It’s one of the oldest types of cookware around, and also one of the most misunderstood.”Noelle Carter, author from shondaland.com
Benefits of Cast Iron
The benefits of using cast iron are:
- It is not reactive with acidic foods like tomatoes and peppers. This property allows food to brown without burning on the bottom of the pan.
- Because of its lower melting point, there is less danger from searing than with other materials. However, when cooking over high temperature the risk of burn-on increases.
- Cast iron retains heat better than stainless steel, which means that foods cooked in cast iron do not overcook as quickly.
- The non-stick properties of cast iron make it ideal for sautéing and stir-frying, especially for people who dislike the squeak caused by the plastic handles of some pans.
- It is strong enough to support heavy pots full of hot liquid even if they were accidentally dropped.
- It is resistant to corrosion because of its relatively low reactivity and high resistance to acids.
- Because it is harder than most metals, it makes sharp knives last longer.
- It gives off large amounts of energy during heating up, so it heats evenly.
- Cast iron is more likely to crack than other metals, but it usually repairs itself easily.
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