Pitting Resistance Equivalent Number (PREN)

Stainless steels and nickel alloys are heavily utilized in many industries thanks to their excellent resistance to corrosion. To help engineers and professionals rank these alloys in term of their pitting resistance, they can use the pitting resistance equivalent number (PREN).

One of the most widely accepted formulas for calculating the PREN is based on the percentage of chromium (Cr), molybdenum (Mo), tungsten (W), and nitrogen (N) present in the alloy. This formula considers the weighted influence of molybdenum and nitrogen, which are known for their substantial impact on pitting corrosion resistance.

PREN = %Cr + 3.3 x (%Mo + 0.5 x %W) + (16 x %N)%3