PREN Pitting Resistance

PREN – Pitting Resistance Equivalency Number

Pitting resistance equivalent numbers (PREN) are a theoretical way of comparing the pitting corrosion resistance of various types of stainless steels, based on their chemical compositions.

The PREN (or PRE) numbers are useful for ranking and comparing the different grades, but cannot be used to predict whether a particular grade will be suitable for a given application, where pitting corrosion may be a hazard.

Actual or specified range compositions can be used and usually involve chromium, molybdenum and nitrogen in the calculations.

Grade

Type

Cr
Min

CR
Max

Mo
Min

Mo
Max

N
Min

N
Max

PREN
Min

PREN
Max

1.4301

Austenitic 304S31

17.5

19.5

 

 

 

0.11

17.5

21.3

1.4362

Lean Duplex

22

24

0.1

0.6

0.05

0.2

23.1

29.2

1.4401/4

Austenitic 316/316L

16.5

18.5

2.0

2.5

 

0.11

23.1

28.5

1.4436

Austenitic 316S33

16.5

18.5

2.5

3.0

 

0.11

24.8

30.2

1.4429

316LN

16.5

18.5

2.5

3.0

0.12

0.22

26.7

31.9

1.4462

Duplex F51

21

23

2.5

3.5

0.1

0.22

30.9

38.1