Where does rust come from? How does it begin to form and why only on certain metals?
In: Chemistry
Rust is Iron (III) oxide. It can only happen on certain metals because it can only happen when iron is present.
Iron (III) oxide is a much weaker chemical than whatever Iron alloy (like steel) the material was made of, so it very easily chips away. That’s what gives it the “eating away” effect. The oxide can only form very close to the surface, but then that can chip away, so more iron can rust.
Iron (II) oxide is less common, but its stronger, and has a distinct black color, rather than the red of rust.
Other metals also oxidize, but they all have wildly different properties. The Statue of Liberty, for example, is made out of copper, so over time, it has turned the distinct green color of copper oxide, but copper oxide doesn’t chip away like rust does.
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