How does cast iron resist rust compared to wrought iron?

Cast iron and wrought iron are both popular materials known for their durability and strength, but they differ significantly in their resistance to rust. Cast iron resists rust better than wrought iron due to its higher carbon content and unique microstructure.

Cast iron contains 2-4% carbon, which forms graphite flakes within its structure. These graphite flakes act as a barrier, slowing down the oxidation process that leads to rust. Additionally, cast iron often has a protective layer of seasoning or coating, further enhancing its rust resistance.

Wrought iron, on the other hand, has a much lower carbon content (less than 0.08%) and a fibrous structure. While it is more malleable and easier to work with, its lower carbon content makes it more susceptible to rust. Wrought iron lacks the graphite barrier found in cast iron, making it more prone to corrosion when exposed to moisture and oxygen.

In summary, cast iron's higher carbon content and graphite microstructure provide superior rust resistance compared to wrought iron. Proper maintenance, such as seasoning or coating, can further extend the lifespan of both materials, but cast iron remains the more rust-resistant option.