On Mon, 1 Mar 2004 17:39:53 -0000, "Ed Rear"
wrote:

Why don't manhole covers, drain grids, etc, rust away?

Steel plate ones do. The old cast iron ones do, but they're so thick
that there's plenty of material to last a long time. Cast iron manhole
covers in roadways more than likely acquire a coating of oil which will
protect them to a large extent as it is polished in to the surface by
tyre action.


--

Dave