“Pitting resistance equivalent number”的意思、由来-开放百科全书

Pitting resistance equivalent number (PREN) is a predictive measurement of a stainless steel's resistance to localized pitting corrosion based on its chemical composition. In general: the higher PREN-value, the more resistant is the stainless steel to localized pitting corrosion by chloride.

PREN is frequently specified when stainless steels will be exposed to seawater or other high chloride solutions. In some instances stainless steels with PREN-values > 32 may provide useful resistance to pitting corrosion in seawater, but is dependent on optimal conditions. However, crevice corrosion is also a significant possibility and a PREN > 40 is typically specified for seawater service.^[1]^[2]^[3]

These alloys need to be manufactured and heat treated correctly to be sea water corrosion resistant to the expected level. PREN alone is not an indicator of corrosion resistance. The value should be calculated for each heat to ensure compliance with minimum requirements, this is due to chemistry variation within the specified composition limits.

PREN Formulas (w/w)

There are several PREN formulas. The most common is PREN = 1 x %Cr + 3.3 x %Mo + 16 x %N

There are a few stainless steels which add tungsten (W), for those the following formula is used PREN = 1 x %Cr + 3.3 ( %Mo + 0.5 x %W ) + 16 x %N

Pitting Resistance Measurement

References

1. ^{{Cite web|url=https://www.offshore-mag.com/articles/print/volume-73/issue-5/productions-operations/pitting-and-crevice-corrosion-of-offshore-stainless-steel-tubing.html|title=Pitting and crevice corrosion of offshore stainless steel tubing|last=Gerhard Schiroky, Anibal Dam, Akinyemi Okeremi, Charlie Speed|first=|date=2013|website=Offshore Magazine|archive-url=|archive-date=|dead-url=|access-date=}}
2. ^{{Cite web|url=http://www.materialsperformance.com/articles/material-selection-design/2016/05/selecting-stainless-steels-for-seawater-pumps|title=Selecting Stainless Steels for Seawater Pumps|last=Kathy Riggs Larsen|first=|date=2016|website=Materials Performance|archive-url=|archive-date=|dead-url=|access-date=}}
3. ^{{cite book|url=https://www.nace.org/cstm/Store/Product.aspx?id=8d3f3286-a246-dd11-889d-0017a446694e|title=08085 High Performance Corrosion Resistant Stainless Steels and Nickel Alloys for Oil & Gas Applications|author=Dirk Aberle and Dinesh C. Agarwal|date=2008|publisher=NACE|isbn=}} Product Number: 51300-08085-SG, Account required - $0.00 No charge
4. ^{{cite book|title=ASTM G48 – Latest : Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution|url=http://www.astm.org/cgi-bin/resolver.cgi?G48|publisher=ASTM|accessdate=28 September 2012}}Full text of standard not available free of charge online but available in libraries