I tried rust and weathering. Also I am fairly new to SciFi.
This was fun to do but it took me out of my comfort zone.
I myself am pleased with the outcome.
The *.stl for RE-04 Robot Engineer is by Romain Dewaest
The *.stl for the Spacehulk HVAC Door Tile is by PalmThreeDee
Both Files are free.
Photos are bad, I know, need to upgrade my photo game.
I am happy to receive feedback.