Pitting Resistance Equivalent Number (PREN)

Written by Jerry Ratzlaff on . Posted in Metal

PERN, a dimensionless number, is a way to measure the pitting corrosion resistance of various types of stainless steel in a chlorine based environment.  The composition of the stainless steel will affect the corrosion resistance.  The higher the number, the more pitting corrosion resistance the material has.


Pitting Resistance Equivalent Number (PREN) Formula

\(\large{ PERN  =  C \;+\; \left( 3.3 * M  \right)  \;+\;   \left( 16 * N  \right)  }\) 
Symbol English Metric
\(\large{ PERN }\)   (Greek symbol alpha) = pitting resistance equivalent number \(\large{ dimensionless }\)
\(\large{ C }\) = chromium in percentage \(\large{ dimensionless }\)
\(\large{ M }\) = moybdenum in percentage \(\large{ dimensionless }\)
\(\large{ N }\) = nitrogen in percentage \(\large{ dimensionless }\)


Piping Designer Logo 1

Tags: Corrosion Equations