904L is a stainless steel alloy that displays high resistance to corrosion, particularly against acidic environments. Additions of copper and carbon give it distinct characteristics, with the copper serving as a strengthening agent against corrosive acids. The small amount of carbon in its compositions gives 904L increased weldability and cleanliness against continual wear and tear. The combination of chromium, nickel, molybdenum and copper in its makeup serve to give 904L exceptional resistance against sulfuric acid. The metal was developed to prevent corrosion where such acids are utilized or applied. Therefore, 904L is approved for use in acid production and concentration, along with the transport of such substances.
In terms of working, both hot and cold working practices can be applied; however, the metal does not harden in response to hot working, only cold. Most common operations like those used to treat grades 304, 316 and 317 stainless steels are also effective on 904L. Additionally, the metal is slow to harden when being worked on and most welding methods are sufficient to yield desired results.