904L was originally developed to withstand environments containing dilute sulfuric acid, and is one of the few stainless steels that, at temperatures up to 95°F (35°C), provides full resistance in such environments within the entire concentration range of 0 to 100%. 904L also offers good resistance to a number of other inorganic acids, such as phosphoric acid and most organic acids. However, acids and acid solutions containing halide ions can be very aggressive, and the corrosion resistance of 317L, 317LMN and 904L may be insufficient.

Fractional distillation of tall oil often needs better material than 316L or even the more frequently used 317LMN. In these hot concentrated caustic solutions, the corrosion resistance is mainly determined by the nickel content of the material. With a nickel content of 25%, 904L has proven to be a good alternative to most conventional stainless steels.

Chemical Properties

Corrosion Resistance

The high content of alloying elements in 904L gives the alloy exceptionally good resistance to uniform corrosion.

Applications

Air Pollution Control — scrubbers for coal-fired power plants

Chemical Processing — process equipment for the production of sulfuric, phosphoric, inorganic and organic acids and the production of phosphate-based fertilizers

Metallurgical Processing — pickling equipment using sulfuric acid

Oil and Gas Production — offshore process equipment

Pharmaceutical Industry — process equipment

Pulp and Paper — processing equipment

Seawater and Brackish Water — condensers, heat exchangers and piping systems