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?