Where does rust come from? How does it begin to form and why only on certain metals?
In: Chemistry
Rust is not the active agent but the outcome of oxidation. Oxygen is the culprit. Oxides are more electrically stable than many pure metals. Aluminum is particularly reactive but the oxide binds to the metal surface protecting the rest of the metal. Iron oxide does not bind so well, so flakes off exposing more of the iron to additional oxygen.
I think a lot of people are answering most of the questions but there’s a little something missing: how does it eat away a metal?
Basically rust is a *different* metal. When the reaction happens to form it, a tiny bit of the iron in the original metal gets converted to rust. So now there is less metal and more rust. Over time, ALL of the metal may get converted to rust.
The rust isn’t really “eating away” the metal. The trick is iron really likes to “stick” to itself so it’s tough and hard. Iron Oxide (what rust is) is NOT that “sticky”, and is very prone to crumbling or falling apart. So as more and more of the metal converts to rust, it’s also turning into something that’s crumbly. Over time stuff wears down the rust, and it makes it look like it’s eating the metal.
But technically it’s more like how a caterpillar becomes a butterfly. The iron is becoming a very crumbly butterfly.
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