Scrap iron is commonly found in Marleybone, just find a nice spawn spot and switch realms constantly, or try the bazaar, although it is kinda rare there
If you can get into Celestia, look around in the District of the Stars. If not, do the Big Ben dungeon in Marleybone and look around the different levels.
where i got all my scrap iron was from the counterwhieghts. go into each one over and over in the very first part and there is two spawn points in each.
