how after restoration of heavily rusted metal objects, they still have so much metal left

Question

I’ve seen a number of videos recently of people restoring very rusted objects, like toys and an anceint historical knife, where the rust seems to have eaten most of the metal. However, after restoration, the object seems good as new and don’t seem to have lost any significant amount of mass even though you’d expect there to be nothing left. How is this even possible?

In: 3

Answer 1

Rust is iron oxide; that is, iron atoms combine with oxygen atoms from the air. Furthermore, the iron oxide molecules can bind with several water molecules to form hydrated iron oxide. Also, rust is usually flaky and porous; a lot of its volume is just empty space–but microscopic empty space. So most of the volume you see didn’t come from the iron or steel object itself; it came from the atmosphere.