Free specification tool
Choose a sign material from the environment first.
Rule of thumb: aluminium for lightweight coated signs; 304 stainless for many normal architectural environments; 316 for materially higher chloride exposure; brass when visual warmth and ageing character are part of the design.
What this tool does not replace
The result is a specification starting point, not engineering approval. Final grade, thickness, finish, fixings and coating still depend on size, fabrication method, mounting, local exposure and maintenance.