Pitting Resistance Equivalent Number

Pitting Resistance Equivalent Number ( Pren )

The PREN index is a measure for the corrosion resistance of a stainless steel. In the ASTM G48 the detailed test procedures are defined. Generally, the higher the Pren - value, the more corrosion resistant the steel. See also effective sum.

The calculate the PRE value is based on the following formula:

Pren = 1 x % Cr 3.3 x % Mo 16 x % N ( w / w)

Steels with Pren - values ​​above 32 are considered to be resistant to sea water.

A Pren - value ≥ 40 set for duplex steels - Furthermore, in the DIN EN ISO 15156 as well as in the American NACE - for use in hydrogen sulphide environments in oil and gas production. Exception: When a molybdenum content ≥ 1.5% a Pren - value ≥ 30 is allowed.

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

Pren = 1 x % Cr 3.3 x (% Mo 0.5x % W) 16 x % N

• Steel