Using part 87058 in black as a base, I built two sets of 2 articulated TTX well cars. Loaded them with a custom container design I published on Rebrickable last month, which uses the profile brick (1x2 and 1x4) as the base for the walls - seems to give the right corrugated steel look.
Decals are from OKBrickWorks.
Looking at the pictures I might need to raise the end trucks/bogies by a plate - did notice this all the time I ran them on my tracks, but on the pictures it seems the cars are not fully level.
TTX Well Car with Containers by Phil B, on Flickr