I am going to build a fire pit, and ran into a few difficulties with conflicting things I have read online. When looking up various DIY projects or 'how to' videos on building a fire pit, a galvanized steel ring is set on the inside of the brick ring. I have read that heating up galvanized steel releases dangerous fumes, and also read that the zinc layer on the steel will be removed at under 400 degrees F. We know a bonfire will vary in temperature, but a few sources I have read say over 1500 degrees F. Steel melts at around 2500 degrees F, so I imagine the fire ring would not end up melting. Does the thickness of the ring have an impact on how effective it is containing the fire? Is using this galvanized steel ring safe / smart / required at all? If so, I was planning on buying steel sheets and riveting them together to build the ring myself as it is cheaper. What are my alternatives?
Galvanized gives no benefit. However.the tiny mount of zinc oxide produced would be no problem . I would suggest a local weld shop may have some stock to make you something. Material at least 1/8" ( 3 mm) thick if you want it to last awhile. Stainless steel is pretty common, either the magnetic ( like auto exhaust) or non-magnetic. Stainless would not need to be as thick. Try a local junk yard.Bolts would be much more practical than trying to rivet. If you could find it, short length cut from large pipe like 24" diameter. Or , the old stand-by, 55 gal drum , cut off a foot of drum.
I answered your question. 1 Steel is a better choice than galvanized for the reason you gave. 2 A weld is preferred to bolts. What is it you need help with cutting steel or, using a drill bit? Making a circle is easy. You also need fire rated paint if you don't want rust. I also gave other options, including purchase of one, that will not rust for a long time. It also has no risk of fumes. Grass removal is also key. I guess you need to be more specific.