The Pitting Resistance Equivalence Number (PREN) is a measure of relative pitting corrosion resistance of stainless steel in a chloride-containing environment.
Higher PREN values indicate greater corrosion resistance.
The Ferritic, Austenitic & Martensitic Stainless Steel grade formula for PREN is:
PREN = %Cr + 3.3 x %Mo + 16 x %N
The Duplex SS grade formula for PREN is:
PREN = %Cr + 3.3 x %Mo + 30 x %N
| % Cr | %Mo | %Ni | %N | PREN | |
|---|---|---|---|---|---|
| 410 | 11.5 - 13.5 | 0.75 | 11 | ||
| Hardtec | 13 | 1-2% | 16 |
| % Cr | %Mo | %Ni | %N | PREN | |
|---|---|---|---|---|---|
| 304 | 18.0 - 20.0 | 8-10.5 | 0.1 | 19 | |
| 316 | 16.0 - 18.0 | 2.0 - 3.0 | 10.0 - 14.0 | 0.1 | 24 |
| 316LHiMo (Bumax) | 16.0 - 18.0 | 2.5 - 3.0 | 10.0 - 14.0 | 0.1 | 25 |
| 254SMO (6Mo) | 20.0 | 6.1 | 18.0 | 0.2 | 43 |
| % Cr | %Mo | %Ni | %N | PREN | |
|---|---|---|---|---|---|
| 2205 | 22.0 - 23.0 | 3.0 - 3.5 | 4.5 - 6.5 | 0.14 - 0.20 | 36 |
| 2507 | 24.0 - 26.0 | 3.0 - 5.0 | 6.0 - 8.0 | 0.24 - 0.35 | 41 |
If the PREN value for a SS is over 40, the SS should be fully resistant to localised corrosion (pitting/crevice corrosion) when immersed in seawater.
NB:This information is provided as a guide only. Anzor does not accept liability for the application of this information.
For advice about stainless steel contact the Nickel Institute.
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