904L, 254SMO, etc. Super austenitic stainless steels are applied in fields such as seawater desalination, flue gas desulfurization, and chemical equipment.

Both are super austenitic stainless steels, specially designed to handle all kinds of "severe corrosion that ordinary stainless steel cannot resist". Simply put, 904L is a "time-honored expert in dealing with moderately strong acids", while 254SMO is a "modern champion in resisting chloride ion corrosion".

The core difference lies in the Pitting Resistance Equivalent Number (PREN): 904L has a PREN of approximately 34–36, whereas 254SMO reaches as high as 42–44, meaning 254SMO’s resistance to pitting corrosion from brine (chloride ions) is several times that of 904L.

A comparison of their specific properties and applications is as follows:

· 904L (classic acid-resistant steel): Contains high nickel (25%) and high molybdenum (4.5%), with added copper. It performs excellently in dilute sulfuric acid (concentration < 70%), phosphoric acid and organic acids, but is sensitive to chloride ions. It is mainly used in sulfuric acid/phosphoric acid storage tanks, flue gas desulfurization (FGD) pipelines, seawater cooling systems, and also in high-end watches and jewelry for its aesthetic appeal. · 254SMO (modern high-molybdenum steel): Contains up to 6% molybdenum and nitrogen. It specializes in high-concentration chloride ion environments (such as seawater and brine), with far stronger crevice corrosion resistance than 904L and higher strength. It is mainly used in seawater desalination equipment, offshore oil and gas platforms, paper bleaching, power plant condensers and other harsh industrial