The range of duplex stainless steel allows them to be matched for corrosion resistance with the austenitic stainless steel and ferritic stainless steel grades. There is no single measure of corrosion resistance. However, it is convenient to use the Pitting Resistance Equivalent Number (PREN) as a means of ranking the grades. PREN = %Cr + 3.3 x %Mo + 16 x %N The following table shows how the duplex stainless steel compare with some austenitic stainless steel and ferritic stainless steel grades.
GradeEN No/UNSTypeTypical PREN4301.4016/ S43000Ferritic stainless steel183041.4301/ S30400Austenitic stainless steel 194411.4509/ S43932Ferritic stainless steel19RDN 9031.4482/ S32001Duplex stainless steel 22316 1.4401/ S31600Austenitic stainless steel 244441.4521/ S44400Ferritic stainless steel24 316L 2.5 Mo1.4435Austenitic stainless steel 262101 LDX 1.4162/ S32101Duplex stainless steel2623041.4362/ S32304Duplex stainless steel26DX22021.4062/ S32202Duplex stainless steel27 904L1.4539/ N08904Austenitic stainless steel342205 1.4462/ S31803/ S32205Duplex stainless steel35Zeron 100 1.4501/ S32760Duplex stainless steel41Ferrinox 255/ Uranus 2507Cu1.4507/ S32520/ S32550Duplex stainless steel 4125071.4410/ S32750Duplex stainless steel436% Mo1.4547/ S31254Austenitic stainless steel44
It must be emphasised that this table is only a guide to material selection. It is always important to assess the suitability of a particular with a full knowledge of the corrosive environment.
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