254SMO has a higher PRE (Pitting Resistance Equivalent) of approximately 42.5 vs. 32 for 904L—making it significantly more resistant to pitting and crevice corrosion in chloride environments.
904L has higher nickel content (23–28%) compared to 254SMO (17.5–18.5%), giving it better resistance to reducing acids such as sulfuric acid at moderate concentrations.
254SMO offers higher mechanical strength—yield strength of 310 MPa vs. 220 MPa for 904L
904L is generally less expensive than 254SMO due to lower molybdenum content.
For seawater, chloride-heavy environments, and FGD systems: 254SMO is the better choice.
For sulfuric acid, phosphoric acid, and mixed acid service, 904L is often more suitable.