904L is an ultra-low carbon, high-alloy austenitic stainless steel. The core advantage of 904L basket type strainers is their exceptional corrosion resistance in harsh environments such as dilute sulfuric acid and chloride-containing media, and their ease of machining and welding.
① Freeman Valve's 904L basket type strainers have high molybdenum (Mo: 4~5%) and copper (Cu: 1~2%) content, significantly improving their resistance to reducing acids (such as sulfuric acid and phosphoric acid) and halides (such as chloride ions);
② Freeman Valve's 904L basket type strainers perform excellently in media such as dilute sulfuric acid, boiling phosphoric acid, and organic acids, exhibiting outstanding resistance to pitting and crevice corrosion.
Freeman Valve's 904L basket type strainers are suitable for environments containing chloride ions (such as seawater and chloride solutions), exhibiting superior resistance to stress corrosion cracking compared to conventional austenitic stainless steels.
Freeman Valve's 904L basket type strainers maintain stability at high temperatures and can withstand short-term environments up to approximately 400°C.
In strong oxidizing acids such as nitric acid, 904L basket type strainers actually have lower corrosion resistance than 304L or 316L valves with lower molybdenum content.
Improper welding or heat treatment of 904L basket type strainers can easily lead to carbide precipitation, requiring solution treatment (rapid cooling at 1100~1150°C) to restore performance.
For example: dilute sulfuric acid storage tanks, pipelines, heat exchangers (especially for sulfuric acid with a concentration ≤10%, exhibiting excellent corrosion resistance at temperatures ≤40℃).
For example: seawater cooling systems, salt chemical evaporators, chlorination reactor linings.
For example: acetic acid and formic acid production equipment, preventing localized corrosion.
For example: flue gas desulfurization (FGD) system components, acidic wastewater treatment equipment.
For example: crystallizers and condensers used in high-temperature acetic acid media.
For example: reaction vessels and pipelines for high-purity pharmaceuticals (resistant to cleaning agent corrosion).
① The pitting equivalent value (PREN≈33-35) of the 2205 basket type strainers is higher than that of the 904L basket type strainers (PREN≈32-34), and the nitrogen content further enhances its resistance to pitting corrosion in high-concentration, high-temperature chloride ion environments (such as high-chlorinated brine in deep well oil production and seawater above 60℃).
② The high nickel + copper content of the 904L basket type strainers results in a passivation film with significantly greater stability than that of the 2205 basket type strainers in reducing media containing chloride (such as dilute sulfuric acid + chloride ion mixtures), without exhibiting the phase imbalance problem common in duplex steels.
① Stress corrosion cracking under chloride ion conditions is a common failure mode for 2205 basket type strainers, but the high nickel content of 904L basket type strainers significantly reduces this susceptibility. 2205 basket type strainers also exhibit better SCC resistance than ordinary austenitic steels such as 316L basket type strainers, but under the same chloride ion concentration and stress conditions, their long-term stability is slightly lower than that of 904L basket type strainers.
① 904L basket type strainers require no heat treatment after welding and have good low-temperature toughness, making them suitable for polar and marine environments.
② 2205 basket type strainers require controlled heat input during welding to avoid excessive ferrite content, but their high strength (tensile strength ≥620MPa, more than 1.2 times that of 904L basket type strainers) makes them more suitable for high-pressure + high-chlorine composite operating conditions (such as high-pressure seawater pipelines).