Question

material used for making ducts is

Answer 1

It may be made by Steel which is galvanised or may be coated with a magnetic material.
Hope it'll be helpful.

Answer 2

here is your answer is

the materiald for making ducts is

- wallproofing , galvanized steel ,aluminium, polyurethane and phenolic insulation panels , fiberglass duct board , flexible ducting , fabric ducting , vibrating isolators etc .