what is a pren standard
Pitting resistance equivalent number (PREN) is a measurement of the corrosion resistance of various types of stainless steel.Exact testing procedures are specified in the ASTM G48 standard. In general: the higher PREN-value, the more corrosion resistant the steel.The PREN-value is calculated using the following formula: PREN = 1 x %Cr + 3.3 x %Mo + 16 x %N (w/w) Steels with PREN-values above 32 are considered seawater (corrosion) resistant.urthermore a PREN-value â¥ 40 for duplex steels is called for in the DIN EN ISO 15156 as well as the American NACE â a standard for use in hydrogen sulfide environments known in the oil and gas extraction industries. Exception: stainless steels with molybdenum content â¥ 1.5% may have a PREN-value â¥ 30.