PREN

The PREN index ( Pitting Resistance Equivalent Number ) is a measure of the corrosion resistance of stainless steel . In the ASTM G48, the closer test methods are defined. In general, the higher the PREN value, the more corrosion-resistant the steel. See also effective sum .

The PREN value is calculated using the following formula:

PREN = 1 ×% Cr + 3.3 ×% Mo + 16 ×% N (w / w)

Steels with PREN values ​​above 32 are considered to be seawater resistant.

Furthermore, in DIN EN ISO 15156 and in the American NACE - for use in environments containing hydrogen sulfide in oil and gas production - a PREN value ≥ 40 for duplex steels is specified. Exception: With a molybdenum content ≥ 1.5%, a PREN value ≥ 30 is permitted.

In these standards, the calculation of the PREN value, taking into account tungsten [W] in the alloy, is defined as follows:

PREN = 1 ×% Cr + 3.3 × (% Mo + 0.5 ×% W ) + 16 ×% N

Web links

• Calculation of pitting resistance equivalent numbers (PREN) (accessed March 4, 2016)