I hope I don't get any pee-pee on me from stepping into this
, but I think the confusion is regarding tubing vs. solid bar stock. Almost all small, thin-wall tubing is made via a process sometimes called CREW (cold-rolled, electric resistance welding). The process starts with hot-rolled flat stock, and it is reduced thinner via cold-working, then cold-formed to final shape (round, square, or rectangular) and welded. The mill scale comes off during the cold reduction and the cold-forming processes, so it has a clean finish. On the other hand, bar stock can be either hot-rolled or, as AirborneTexasRanger pointed out, cold-rolled. It's the hot-rolling process where mill scale forms. I think Mr. Blaine had tubing in mind, but I think freedom_in_4low actually used hot-rolled bar stock for the railings. After all, it would be very difficult to mistake the clean surface finish of cold-rolled steel for mill-scale. Depending on the skill of the mill operator and how long the steel has say in inventory, it can actually have a shine to it.