Electric Metallic Tube Conduit

I think it is cast actually. Not positive though.

I have seen both types at home depot. You really have to inspect the pipe in person I have found,

Go to your local metal supply store, and grab aluminium tubing .... you won't have to worry about weight or corrosion.

There is some high falutin' metal conduit that has a coated interior to protect the wire that runs through it. I've only heard about it and I heard that it is well over two dollars for a ten foot piece.