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How to compute PREN in Python using UliEngineering

You can easily compute the Pitting Resistance Equivalent Number (PREN) using the UliEngineering Python library:

pren.py
from UliEngineering.Chemistry.PREN import pren

# Compute PREN for 304 stainless steel (18% Cr, 8% Ni, 0% Mo)
pren_value = pren({"Cr": 18.0, "Ni": 8.0, "Mo": 0.0})
print(f"PREN (304 steel): {pren_value:.1f}")

# Compute PREN for 316 stainless steel (17% Cr, 12% Ni, 2.5% Mo)
pren_value = pren({"Cr": 17.0, "Ni": 12.0, "Mo": 2.5})
print(f"PREN (316 steel): {pren_value:.1f}")

# Compute PREN for 904L stainless steel (20% Cr, 25% Ni, 4.5% Mo)
pren_value = pren({"Cr": 20.0, "Ni": 25.0, "Mo": 4.5})
print(f"PREN (904L steel): {pren_value:.1f}")

Example output

pren_output.txt
PREN (304 steel): 18.0
PREN (316 steel): 24.5
PREN (904L steel): 33.5

The Pitting Resistance Equivalent Number (PREN) is a measure used to predict the pitting corrosion resistance of stainless steels and other corrosion-resistant alloys. Higher PREN values indicate better resistance to pitting corrosion in chloride-containing environments. This is essential for material selection in chemical processing, marine applications, and any environment where localized corrosion is a concern.

The PREN is computed using the formula: $\text{PREN} = %Cr + 3.3 \times %Mo + 16 \times %N$, where $%Cr$, $%Mo$, and $%N$ are the weight percentages of chromium, molybdenum, and nitrogen respectively. Some formulations also include nickel with a coefficient, but the standard formula focuses on these three key elements for pitting resistance.

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