I compared the black ducting for wood stoves with regular galvanized ducting and found that they are both 24 gauge and I noticed they are both steel since both tug magnets. There is quite a large price difference in addition to not as much stocked variety for the black pipe. The galvanized is ubiquitous with all sorts of adapters and sizes available.
Black pipe is available only in 6 and 8 inch diameters. I had an idea of spray painting the galvanized duct with high temperature resistant RustOleum. Would this work?
Best Answer
24-gauge is 24-gauge. However, the the silver type round pipe is coated with a rather inexpensive galvanizing coating. This coating is to inhibit rust. The galvanizing keeps oxygen and moisture away from the raw metal.These elements will discolor the metal, causing the metal to oxidize and rust, thus shortening the life of the metal. Now for the down side of you situation. When the galvanized coating gets too hot as in when used as a wood stove chimney vent the the galvanizing burns off and in the process produces a dangerous gas. If this gas is inhaled the result will be sickness and even death.
Sorry you are going to have to put up the money for the black stuff. Top coating this with paint no matter the quality is not enough to ensure protection against this off gassing.