Hi, I just picked up several sections of pipe from the junkyard, but I
can't really peg what it is known as. The sections are about 4"
long. It is a dark gray steel with a little bit of red rust. The
outer diameter is about 6-1/8" and the wall thickness is about 0.11".
The more clean pieces exhibit a slightly blue sheen. Some of the
pieces are wrapped with one or more layers of very light aluminum
foil. The seam is visible but has been ground down slightly concave,
probably by machine. I've looked for about an hour on the internet
but can't find any pipe size charts that contain those dimensions.
Does anyone know what this stuff is called?

--zeb