Pitting resistance equivalent number
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.[1] 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.
Furthermore a PREN-value ≥ 40 for duplex steels is called for in the DIN EN ISO 15156 as well as the American NACE – a standard for use in hydrogen sulfide environments known in the oil and gas extraction industries. Exception: stainless steels with molybdenum content ≥ 1.5% may have a PREN-value ≥ 30. In these norms the PREN-value takes into account tungsten [W] in the alloy and is defined with the formula: PREN = 1 · %Cr + 3.3 ( %Mo + 0.5 · %W ) + 16 · %N
References
- ↑ Lua error in package.lua at line 80: module 'strict' not found.Full text of standard not available free of charge online but available in libraries
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