The iron had long since rusted and corroded, leaving scraps of pipe strewn across the tops of the forges.

In places the iron had so rusted that it fell away to powder at the touch.

Change of color (for example, silver to reddish-brown when iron rusts).

In the presence of dry oxygen, dry iron rusts very slowly.

The iron rusts fast when it's cut in bits where the air can get at it.

But what of the knowledge that iron rusts when left out in the rain?

The iron had rusted over time without proper maintenance.

While the stonework could date-doubtless did date-from the Old Kingdom, iron would have rusted away long since in this dank environment.

When iron rusts into iron oxide, it lets loose an electron.

Over the eons, the iron had rusted down into a sort of damp red mud that outlined the enormous dimensions of the fallen structure.