duplex stainless steel

Corrosion properties of duplex stainless steel S32205 plate




It is stainless steel that contains about a 25% increase in chromium (Cr), about 5% decrease in nickel, and a 1:1 two-phase mixture of austenite and ferrite.

It features high strength and high corrosion resistance and is also excellent in stress corrosion cracking. Therefore, it is used in a wide range of applications such as sluices, tunnels, sewer facilities, seawater desalination plants, and chemical tankers.

Duplex Plate is widely used in industries and components such as steelmaking, papermaking, desalination equipment, firewalls, bridges, pressure vessels, heat exchangers, turbine blades, and for transmission shafts for marine systems.

The higher the content of chromium, molybdenum and nitrogen alloying, the better corrosion resistance property Duplex 2205 Plate has. When duplex stainless steel contains at least 30% ferrite in the microstructure, its corrosion resistance is much better than that of austenitic stainless steel. However, because ferrite is sensitive to hydrogen embrittlement, duplex stainless steel 2205 does not currently have high corrosion resistance in environments and applications where hydrogen penetrates the metal and causes hydrogen embrittlement.

Pitting corrosion resistance

In specific chloride environments, each grade of stainless steel can be described by its critical point corrosion temperature (CPT), above which pitting corrosion begins to occur and grows to the naked eye within 24 hours. There is a possibility that Super Duplex Plate have less corrosion resistance below the  required temperature. It represents a particular stainless steel grade and the environment.

Grain boundary corrosion resistance

Intergranular corrosion often appears in joint gaskets, bottom sediments, and bolt joints. There is a similar critical temperature for intergranular corrosion. The critical crevice corrosion temperature (CCT), is mainly depends on the stainless steel specimen, chloride environment, and crevice properties (compactness, length, etc.). Due to the shape of the gap and the fact that it is challenging to present the same gap size in practice, the CCT measurement data is more diversified than the critical point corrosion temperature (CPT). CCTS tends to be 15-20°C lower than CPT for the same grade and corrosive environment.

Stress corrosion resistance

Like many materials, Duplex Steel Sheet are susceptible to stress corrosion cracking under certain conditions. This can occur at elevated temperatures, in chloride-containing environments, or media sensitive to hydrogenolysis. In Environmental conditions stress corrosion cracking can occur in duplex stainless steel plates.

Tests have demonstrated superior corrosion resistance compared to austenitic and ferritic stainless steels. The sample of plates used for the 2205 stainless steel test has a size of 1600 * 2500 * 10mm, supplying a wide range of metals for different applications.

The key to the duplex stainless steel welding material is the extremely high N content. In welding of Duplex Steel Plate, porosity defects such as blowholes, pits and gas grooves due to N are more likely to occur than in general austenitic stainless steel. When welding duplex stainless steels, it is basically recommended to select welding materials of the same grade and, in some cases, of higher grades.