904L is a high-alloy austenitic stainless steel with low carbon content. The grade is intended for use under severe corrosive conditions. It has been application proved over many years and was originally developed to resist corrosion in dilute sulfuric acid. It is standardized and approved for pressure vessel use in several countries. Structurally, 904L is fully austenitic and is less sensitive to precipitation ferrite and sigma phases than conventional austenitic grades with high molybdenum content. Characteristically, due to the combination of relatively high contents of chromium, nickel, molybdenum and copper 904L has good resistance to general corrosion, particularly in sulfuric and phosphoric conditions.