Stainless Steel ASTM A790/Uns S32750 Pipes for Desalination Plants Duplex Steel 2507 Tube

General Corrosion
The high chromium and molybdenum content of 2507(F53) makes it extremely resistant to uniform corrosion by organic acids like formic and acetic acid. 2507(F53) also provides excellent resistance to inorganic acids, especially those containing chlorides.

In dilute sulfuric acid contaminated with chloride ions, 2507(F53) has better corrosion resistance than 904L, which is a highly alloyed austenitic steel grade specially designed to resist pure sulfuric acid.

Stainless steel of type 316L (2.5%Mo) cannot be used in hydrochloric acid due to the risk of localized and uniform corrosion. However, 2507(F53) can be used in dilute hydrochloric acid. Pitting need not be a risk in the zone below the borderline in this figure, but crevices must be avoided.

Intergranural Corrosion
2507's low carbon content greatly lowers the risk of carbide precipitation at the grain boundaries during heat treatment; therefore, the alloy is highly resistant to carbide-related intergranular corrosion.

Stress Corrosion Cracking
The duplex structure of 2507(F53) provides excellent resistance to chloride stress corrosion cracking (SCC). Because of its higher alloy content, 2507(F53) is superior to 2205 in corrosion resistance and strength. 2507(F53) is especially useful in offshore oil and gas applications and in wells with either naturally high brine levels or where brine has been injected to enhance recovery.

Pitting Corrosion
Different testing methods can be used to establish the pitting resistance of steels in chloride-containing solutions. The data above were measured by an electrochemical technique based on ASTM G 61. The critical pitting temperatures (CPT) of several high-performance steels in a 1M sodium chloride solution were determined. The results illustrate the excellent resistance of 2507(F53) to pitting corrosion. The normal data spread for each grade is indicated by the dark gray portion of the bar.

Crevice Corrosion
The presence of crevices, almost unavoidable in practical constructions and operations, makes stainless steels more susceptable to corrosion in chloride enviroments. 2507(F53) is highly resistant to crevice corrosion. The critical crevice corrosion temperatures of 2507(F53) and several other high-performance stainless steels are shown above.


Chemical Composition

The chemical composition of stainless steel grade Super Duplex 2507(F53) is outlined in the following table.

The physical properties of stainless steel grade Super Duplex 2507(F53) are tabulated below.

Preheating of 2507(F53) is not necessary except to prevent condensation on cold metal. The interpass weld temperature should not exceed 300°F or the weld integrity can be adversely affected. The root should be shielded with argon or 90% N2/10% H2 purging gas for maximum corrosion resistance. The latter provides better corrosion resistance.

If welding is to be done on only one surface and post-weld cleaning is not possible, GTAW is suggested for root passes. GTAW or PAW should not be done without a filler metal unless post-weld cleanup is possible. A heat input of 5-38 kJ/in. should be used for SMAW or GTAW. A heat input of about 50kJ/in. can be used for SAW.

Super Duplex 2507(F53) is widely used in the following sectors:

Products made using Super Duplex 2507 include: