Steel and iron are two versatile materials. They are used to make bridges, buildings, automobiles, aircraft, fasteners, gates and more. While they share some similarities, however, they steel and iron aren’t the same.
Composition
Steel and iron have different compositions. Iron is a metal element with the atomic number 26. It accounts for over one-third of the Earth’s total mass, making it very common.
Unlike iron, steel isn’t an element. Rather, it’s an iron alloy. Steel consists primarily of iron and carbon, along with smaller amounts of other alloying elements. Some types of steel contain up to 2.14% of carbon, whereas others contain as little as 0.02% of carbon. Regardless, all types of steel consist primarily of iron and carbon.
Porous
Iron is more porous than steel. The porous surface of iron, especially cast iron, allows it to absorb liquid. Cast iron pans, for instance, are popular because they absorb flavorful oils. Steel is less porous. The addition of carbon and other alloying elements creates a more solid, less breathable surface.
Hardness
Steel is harder than iron. Pure iron is relatively soft and ductile. This makes it easy to bend and shape. Steel, on the other hand, is hard and tough. And the more carbon it contains, the harder it will be. High-carbon steel is prized for its superior strength. AISI 1080 high-carbon steel, for instance, has a tensile strength of 140,000 pounds per square inch (PSI).
Corrosion
Steel is better protected against corrosion. Corrosion is a chemical reaction that involves the conversion of a metal or metal-containing alloy into an oxide, such as rust. When exposed to oxygen, metals and metal-containing alloys may develop iron oxide, which is more commonly known as rust.
Steel is less susceptible to rust and corrosion because it often features a protective outer layer. Stainless steel, for example, contains at least 10.5% chromium. Exposure to oxygen allows it to develop a layer of chromium oxide on the surface that protects it from rust and corrosion. With this protective layer, oxygen won’t reach the underlying steel.
Cost
You can expect to pay more for steel. As previously mentioned, one of the key differences between iron and steel is the composition. Iron is a metal element that occurs naturally in Earth’s crust and core, whereas steel is an alloy. Alloys require time and resources to produce. Therefore, steel almost always costs more than iron. These are just a few of the ways that iron and steel differ.