Rust on old cast iron pans is primarily caused by exposure to moisture and oxygen. Cast iron is a porous material, and when it comes into contact with water or high humidity, the iron in the pan reacts with oxygen from the air, leading to the formation of iron oxide, commonly known as rust.
Here's a breakdown of the process that causes rust on cast iron pans:
Exposure to water: When cast iron pans come into contact with water, especially for extended periods, the iron surface begins to oxidize.
Oxygen: The presence of oxygen is essential for the rusting process. When the iron in the pan reacts with oxygen from the air, it forms iron oxide, which is the reddish-brown substance we know as rust.
Acidic or alkaline substances: Foods containing acids or alkaline substances can accelerate the rusting process. They can weaken the protective layer of seasoned oil on the cast iron surface, making it more susceptible to rust.
Improper cleaning and storage: If a cast iron pan is not dried thoroughly after washing, or if it is stored in a damp environment, moisture can accumulate and lead to rust formation.
Preventing rust on cast iron pans:
Seasoning: The process of seasoning involves coating the cast iron surface with a layer of oil and baking it. This creates a natural non-stick coating and protects the iron from direct exposure to moisture and oxygen. Regularly seasoning your cast iron pan helps maintain its non-stick properties and prevents rusting.
Proper drying: After washing the cast iron pan, thoroughly dry it with a towel or place it on the stovetop over low heat to evaporate any remaining moisture. Make sure it is completely dry before storing it.
Avoid soaking: Avoid leaving cast iron pans in water or soaking them for extended periods. Instead, hand wash the pan with minimal water and gentle scrubbing.
Store in a dry place: Store your cast iron pan in a dry place with good air circulation. If storing it in a cupboard or drawer, ensure it is completely dry before putting it away.
Use wooden or silicone utensils: When cooking with cast iron, use utensils made of wood or silicone to avoid scratching the seasoned surface, which can expose the iron to moisture and accelerate rusting.
With proper care and maintenance, including regular seasoning and diligent drying after use, you can prevent rust from forming on your old cast iron pans and keep them in excellent condition for generations.