Duplex Stainless Steel:


Duplex stainless steel refers to Ferrite and Austenite about 50%, generally less phase content of at least 30% of stainless steel,it has the characteristics both of Austenitic and Ferritic stainless steel.

 

Compared with the Ferrite stainless steel, higher toughness, no room temperature brittleness, resistance to corrosion and welding performance are significantly improved

 

Compared with the Austenitic stainless steel, high strength and resistance to pitting corrosion and resistance to chloride stress corrosion has improved significantly.

 

Duplex stainless steel is a new trend of material that used for stainless steel water tank, with more excellent corrosion resistance than other types of stainless steel and much longer lifetime, it is the best choice for stainless steel water tank, and M&T is the the first manufacturer to adopt duplex stainless steel as inner tank material in China.


What is Duplex Stainless Steel?  

                               

·  Austenitic18Cr + 8Ni + (2Mo)  

√ Excellent formability and weldability

√ Good resistance to local corrosion

√ Sensitive to Stress Corrosion Cracking


· Duplex22Cr + 1.5 - 5 Ni

√Combination of austenitic & ferritic structure

√Not sensitive to SCC

√Good weldability and machinability

√High mechanical properties

√Low alloy content – price stable


· Ferritic20Cr + (2Mo)

√No Ni-content - price stable

√Not sensitive to SCC

√Limited welding and elongation properties

   



Pitting Corrosion


Corrosion - Crevice cossosion


                                 

                                  The oxygen content in the narrow 

                                  crevice decrease and the amount of 

                                  acidic corrosion products increase 

                                  Chloride ions destroy the passive

                                  layer.


                                  A galvanic cell is formed between the 

                                  bare metal inside the crevice and the

                                  passive layer outside.


                                  pH decreases and the chloride 

                                  content increases inside the crevice 

                                  The attack grows!


       Duplex  is highly effective 

         resistance against pitting corrosion.





Comparation with SUS304 and SUS316L