Mars Relic Iron Farming Route
One of the best farming routes for Relic Iron is in the Scablands on Mars. There are a number of large buildings in the area with have rooms underneath and on the side of them in which chests containing Relic Iron can spawn. Chests containing Relic Iron can also spawn on the cliffs near the building and in caves under those cliffs. There are more chests containing Relic Iron in the tunnels under the middle area.