On Mon, 20 Dec 2010 03:39:59 -0500, Joe wrote:

I have a galvanized chimney, no bricks, no stones, no tile liner, just
one galvanized sheet metal pipe within another, to keep the outside
cool, and an oil furnace in the basement.

Reading more webpages, I see that maybe one or both layers is
stainless steel, not galvanized.