Do we lose metal forever when it rusts?


If a piece of metal rusts before we can protect it or recycle it, do we lose it forever?

Would a piece of metal just rust away to nothing if just left outside?

What is the chemical change from [insert metal] to rust?

In: Chemistry

Most rusting is from the pure metal becoming oxidized, meaning oxygen from the atmosphere attaches to it and changes it’s chemical properties. Rust can be melted back into metal easily enough, though if a piece of metal rusts into a powder, collecting it all back becomes a challenge. When melting it back, you’ll have impurities that got trapped and will need to remove them to get pure iron back.

Rusting is oxidation, oxygen gas is attacking the metal atoms and chemically binding to them.

Iron oxide specifically has an annoying tendency to crumble to dust so iron and iron-rich alloys can definitely rust away to nothing.

Some other metal oxides stick better and form a protective crust that shields the metal from furher corrosion.

Turning the rust back into pure metal is definitely possible (that’s likely where it came from in the first place), but usually not economically feasible once it’s highly impure and pulverized into orange dust.

No, it’s just Iron molecules bonding with Oxygen.

We can reclaim the Iron and re-forge it into steel with enough rust and additives.

Yes – *if* you can keep the rust around. Rust is just iron that has combined with oxygen, and if you heat the rust enough, it will break the bonds, release the oxygen, and give you pure molten iron. Straightforward enough. In fact, most of the iron we mine out of the ground comes out as some form of iron oxide – chemically similar to rust.

The problem is that iron oxide (i.e. rust) wears away much more easily than iron. That’s why you can polish or scrub it off of metal. The rust becomes dust in the air or water, which makes it very hard to collect and recycle.

Say you dropped an iron pan into a big aquarium and left it there for a long time. Eventually the whole thing would rust and dissolve into the water. You could boil or filter the water and reclaim the rust particles from it, and then melt that back into iron.

But in the real world, mostly the rust is going to get blown away, washed away, or even intentionally scrubbed away as part of the restoration process.

Metals are elements. There are iron atoms, and unless a nuclear change occurs to them they remain iron. Rusting is a chemical change when iron bonds to oxygen. It is still iron, just with oxygen. So no iron is lost. And you can separate the iron and the oxygen.