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Corrosion Resistance - PREN Values

Pitting Corrosion Resistance

The Pitting Resistance Equivalence Number, PREN, is a measure of relative pitting corrosion resistance of stainless steel in a chloride-containing environment.

Higher PREN values indicate greater corrosion resistance.

The Ferritic, Austenitic & Martensitic SS grade formula for PREN is: PREN = %Cr + 3.3 x %Mo + 16 x %N

The Duplex SS grade formula for PREN is: PREN = %Cr + 3.3 x %Mo + 30 x %N


Martensitic Grades
% Cr %Mo %Ni %N PREN
410 11.5 - 13.5 0.75 11

Austenitic & Ferritic Grades
% Cr %Mo %Ni %N PREN
304 18.0 - 20.0 8-10.5 0.1 19
316 16.0 - 18.0 2.0 - 3.0 10.0 - 14.0 0.1 24
316LHiMo (Bumax) 16.0 - 18.0 2.5 - 3.0 10.0 - 14.0 0.1 25
254SMO (6Mo) 20.0 26.1 18.0 0.2 43

Duplex Grades
% Cr %Mo %Ni %N PREN
2205 22.0 - 23.0 3.0 - 3.5 4.5 - 6.5 0.14 - 0.20 36
2507 24.0 - 26.0 3.0 - 5.0 6.0 - 8.0 0.24 - 0.35 41

If the PREN value for a SS is over 40, the SS should be fully resistant to localised corrosion (pitting/crevice corrosion) when immersed in seawater.

NB:This information is provided as a guide only. Anzor does not accept liability for the application of this information.
For advice about stainless steel contact the Nickel Institute.

Find more information about Stainless Steel here:


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