Overview
PREN (Pitting Resistance Equivalent Number) is a calculated index used to compare the relative pitting corrosion resistance of stainless and related alloys based on their chemical composition. It is a ranking tool and not a stand‑alone specification.
How It Works
PREN is commonly calculated from %Cr, %Mo, and %N (and sometimes %W). One widely used form is:
PREN = %Cr + 3.3 × (%Mo + 0.5 × %W) + 16 × %N. Use the calculator to input alloy chemistry and compare results.
Steps:
- Open the PREN Calculator: https://www.rolledalloys.com/pren-calculator/
- Enter the alloying elements requested (Cr, Mo, N, optional W).
- Click Calculate to view the PREN value and compare alloys.
Helpful Tips
Higher PREN generally indicates higher pitting resistance; however, consider crevice corrosion, temperature, fabrication, and service environment as well—PREN is a guide, not a guarantee.
When selecting an alloy for chloride service, consult a metallurgist to confirm suitability beyond PREN alone.
