What is PREN
There are several Pitting Resistance Equivalent Number formulas in different versions of the data, but generally speaking, this formula is the most widely used:
PREN = 1*Cr% + 3.3 * Mo% + 16 * N%.
There is a version of the pitting corrosion resistance equivalent value Pitting Resistance Equivalent Number formula is more accurate: There are a few stainless steels which add tungsten (W), for thosethe following formula is used PREN = 1 x Cr% + 3.3 ( Mo% + 0.5 x W% ) + 16 x N%
PREN Calculator
Formula: Cr + 3.3 * (Mo + 0.5 * W) + 16 * N
Metals with higher PREN values appear to be more resistant to localized corrosion than metals with lower Pitting Resistance Equivalent Number values.
In general, metals with a PREN value greater than 32 can be used to resist seawater pitting corrosion. For safety and stability, materials with a PREN value greater than 40 such as S31254 super stainless steel pipe and 2507 super duplex pipe are often used in the seawater environment and offshore service.
Anti-pitting measurement method:
ASTM G48 standard specifies the precise pitting corrosion test procedure.
The PREN Values of Common Special Metals Are as Follows:
