How does rust work to eat away a metal?

Question

Where does rust come from? How does it begin to form and why only on certain metals?

In: Chemistry

Answer 1

Rust is iron oxide, formed when oxygen reacts with iron. The problem with rust is that it’s less waterproof and airtight than regular iron, so once rust forms, it creates an opening for air and water to get deeper into the metal and create even more rust. Some metals either don’t react with oxygen (gold, for example), or they react with oxygen to form an oxide that is waterproof and airtight (creating a patina). This patina prevents oxygen from penetrating further into the metal, and is sometimes even desirable as it may have certain characteristics like strength and chemical resistance that are superior to the original metal.