904L stainless steel is a high-alloy austenitic stainless steel known for its exceptional corrosion resistance, particularly in harsh and aggressive environments. It is commonly used in industries where strong resistance to chloride-induced pitting, stress corrosion cracking, and general corrosion is critical. Applications include chemical processing equipment, such as tanks, piping, and heat exchangers for handling sulfuric, phosphoric, and acetic acids. It is also used in the oil and gas industry, seawater cooling devices, pollution control systems, and in the production of high-quality components like flanges and fittings. Additionally, 904L is favored in the pharmaceutical and food processing industries for its ability to maintain integrity in highly corrosive environments.

904L stainless steel is generally considered superior to 316 stainless steel in terms of corrosion resistance, especially in highly corrosive environments. 904L contains higher amounts of chromium, nickel, and added elements like molybdenum and copper, which enhance its resistance to chloride-induced pitting, stress corrosion cracking, and acid attack. This makes 904L more suitable for aggressive chemical environments, such as handling sulfuric and phosphoric acids, compared to 316, which performs well in moderately corrosive conditions. However, 904L is more expensive and harder to machine and weld than 316, so it is typically used only when the enhanced corrosion resistance is necessary.

904L stainless steel is equivalent to various international standards and alloys with similar properties. In terms of standards, it is equivalent to UNS N08904, DIN 1.4539, and EN 904L. It is also comparable to Alloy 904L and shares similarities with other high-alloy austenitic stainless steels that offer excellent resistance to corrosion in aggressive environments. While there isn’t a perfect match, other alloys like Super Duplex stainless steel or certain nickel-based alloys may be considered for applications requiring comparable corrosion resistance, especially against chlorides and acids.