Duplex stainless steel is a nonrusting and acid-proof steel. But there are also other characteristics that make it the perfect partner for water treatment applications.
Due to its particular chemical composition, duplex stainless steel is a real jack-of-all-trades. So it does not only suit the demands of the automotive industry: Because of its high resistance against acid and corrosion, duplex stainless steel is used especially where the material is exposed to harsh environments. Besides the chemical sector, this is most of all the water industry.
Norm DIN EN 10312 provides information about technical delivery conditions of „Welded stainless steel tubes for the conveyance of water and other aqueous liquids.“ There you can read, that the duplex steel grades 1.4362 and 1.4462 (2205) should be used preferably. In general, duplex steel sections with this grades are suitable for systems of water distribution and storage. A comparison with other kinds of stainless steels explains, why.
Due to its alloy, duplex combines the characteristics of austenitic and ferritic stainless steel. Compared to other stainless steels, the alloy elements of duplex stainless steel are so well-matched, that a higher resistance against stress corrosion cracking occurs. For example, duplex steel grade 1.4462 exceeds common austenitic stainless steels grades like 316L (1.4404) or 316Ti (1.4571). In fact, the duplex grades come with a lower nickel content, but with a higher content of molybdenum, this makes them to price-competitive alternative to common stainless steel, especially when taking advantage of the possible weight savings due to the higher yield. The higher level of yield strength is reached by adding nitrogen to the alloy, which leads as downside to a lower ductility and formability of the material.
In water treatment, higher yield-strength only plays a minor part. Nonetheless, there are applications where contractors preferably use duplex steel sections. That is especially the case, where the advantage of the higher mechanical properties are transferred by the designer into a lighter structure. This leads to significant savings of weight and material costs.
Due to its higher corrosion resistance, contractors use duplex steel under as well as above water. Thereby you can see its resilience in wind and weather. Duplex stainless steel also comes into action near salt water, because there is a higher risk of corrosion. Hence, duplex is a preferred material for applications near the sea. For cooling with sea water, or salt water treatments, super duplex stainless steel in grade 1.4410 (2507) is perfect.
Furthermore, duplex is known to be acid-proof. Hence, it is a unique material for waste water treatment plants. That is where waste waters with highly different pH-values meet, what creates an extreme environment for stainless steel profiles. Super duplex proves to be especially resistant. One cannot only use it in an environment containing chloride, but also phosphoric and organic acids without damages to the material.
At Montanstahl, we produce the most different special profiles, so we can meet our customer’s needs individually. For that, we can provide special shapes made of various materials. Amongst them are also of course duplex stainless steel, super duplex and lean duplex. Due to that, we contribute to the water treatment with its special requirements.