Q: Which material would be better suited for a nitric acid environment (Hastelloy C276 or Inconel)? The screws would not be submersed in the acid, but in a room where the screws would be around the fumes.
A: For nitric acid fumes Hastelloy C276 bolts would be the go-to material unless you are at high temperatures. In that case, Hastelloy C22 fasteners may be a better option. Check out the iso-corrosion curves shown on this page: https://www.extreme-bolt.com/