Why Does Metal Rust

You have probably seen reddish-brown rust on old nails, bikes, or fences. Rust forms when iron meets water and oxygen from the air. A chemical reaction called oxidation slowly turns the shiny metal into crumbly, orange-brown rust. Rust weakens metal over time.

How Rust Forms

Iron atoms on the surface of metal react with oxygen molecules in the air. Water speeds up this reaction. The iron and oxygen combine to form iron oxide, which we call rust. Salt also speeds up rusting, which is why cars rust faster near the ocean. Rust keeps eating deeper into the metal if it is not stopped.

Preventing Rust

People use many methods to prevent rust. Painting metal puts a barrier between the iron and the air. Galvanizing coats iron with a layer of zinc for protection. Stainless steel is made by mixing iron with chromium, which resists rusting. Keeping metal dry also helps because rust needs water to form.

Fun Facts

• Rust can make iron swell to up to six times its original size.
• The Statue of Liberty turned green because its copper skin oxidized, similar to how iron rusts.
• Rust never sleeps. It keeps spreading as long as iron is exposed to water and air.

Did You Know?

Rust costs the United States hundreds of billions of dollars every year in damage to bridges, cars, and buildings. Engineers are always looking for better ways to protect metal from rusting!