You can find all crates in all main areas in Dredge The Iron Rig with the help of the maps below.
All Iron Rig Crates
This guide/maps contain some minor spoilers regarding the events in the iron rig dlc and some pursuits found in the main game.
If you want to know only the location of Dredge the Iron Rig crates and how the map is altered by the events in the dlc, please refer to the general map and the the marrows section.
General Map
The Marrows
Gale Cliffs
? = figure in gold
Stellar Basin
? =Figure in gold
Twisted Strand
? =Figure in purple
Devil´s Spine
? =Figure in red