Rust

chemistry · iron · corrosion · oxidation

Iron gets sick. When iron is exposed to oxygen in the air or moisture, it undergoes a chemical reaction that weakens and transforms it into rust. It's like iron's way of breaking down when it gets too wet and exposed.

Water makes it happen. Rust needs water or moisture in the air to form, which is why cars and metal objects rust faster near the ocean or in rainy climates. Without water, iron won't rust even if it's sitting in dry air.

The color tells the story. Rust is usually reddish-brown because it's a special form of iron called iron oxide. This color comes from the way iron atoms bond with oxygen atoms during the rusting process.

A slow transformation. Rust is actually a completely new substance made when iron and oxygen combine, not just a coating on top. It continues to spread and eat away at the metal if it's not stopped or painted over.