It isn't, but that's beside the point, which is that there's little enough difference between iron and steel that the Eiffel and Blackpool towers being made of wrought iron doesn't prevent them demonstrating that large structures engineered in steel are quite possible to maintain given the requisite investment in actually doing the maintenance.

(Saying that, for example, 300-series stainless, around 30-40% chromium and nickel, "is iron", could be fairly criticized this way. Mild steel not so much, and that was what I really had in mind with the statement, although I concede I didn't say so.)