I was recently asked if we could make an unpainted carbon steel drum with no coatings of any kind, just bare steel… and oh, one more thing, there could be no rust. The answer to the request is very easy, no (a polite no, of course). There are basic laws of chemistry we can’t defy, rust is one of them.
4Fe + 3O2 + 6H2O → 4Fe(OH)3.
Steel rusts because of a chemical reaction when exposed to water and oxygen in the air. Steel is made from iron, and when iron comes into contact with water and air, a process called oxidation occurs. During this process, the iron reacts with the oxygen in the air and forms a new substance called iron oxide, which we know as rust.
When steel gets wet, such as from rain, moisture, or humidity, the water provides the necessary ingredient for the chemical reaction to take place. The oxygen in the air combines with the iron in the steel, causing it to rust. Rust appears as a reddish-brown substance that forms on the surface of the steel.
Rust is not good for steel because it can weaken the metal over time. That’s why it’s important to protect steel from moisture and air by using coatings like paint, zinc, or other unique materials that create a barrier. These coatings act as a shield, preventing water and air from reaching the iron in the steel and reducing the chances of rust formation.
So, that’s why steel rusts! Isn’t science fascinating?