Back to GlossaryMetallurgy
PREN
Pitting Resistance Equivalent Number — a formula used to predict the pitting corrosion resistance of stainless steels based on their chemical composition: PREN = %Cr + 3.3(%Mo) + 16(%N).
Understanding PREN
PREN (Pitting Resistance Equivalent Number) is a widely used index to compare the pitting corrosion resistance of different stainless steel grades. A higher PREN indicates better resistance to localized corrosion.
Formula
PREN = %Cr + 3.3 × %Mo + 16 × %N
Typical Values
- 304L: PREN ~18
- 316L: PREN ~24
- 2205 Duplex: PREN ~35
- 2507 Super Duplex: PREN >40
- 254 SMO: PREN ~43
For seawater applications, a minimum PREN of 40 is typically specified.