The acronym PREN stands for Pitting Resistance Equivalent Number. It is an approximated number calculated from a formula based upon a material’s chemical composition that estimates a material’s resistance to pitting. This number is primarily used for stainless steels being used particularly in chloride-rich environments.
Pitting corrosion is a localized form of corrosion that causes small, deep holes or pits to form on a metal surface. This type of corrosion is highly localized and can lead to rapid material failure with minimum material loss.
Causes of Pitting:
Check out several types of pitting below:
The following equation is the PREN Formula:
The higher the PREN value, the better the alloy resists pitting corrosion. Please note that for this specific type of corrosion nickel & copper content offer minimal to no corrosion resistance.
A minimum PREN value of 32 is considered to protect against seawater pitting corrosion.
Check out Nickel Systems PREN Values for our Stainless Steel & High Nickel Alloys:
UNS Number | Material | PREN |
UNS N06600 | Inconel® 600 | 16 |
UNS N07750 | Hastelloy® X750 | 16 |
UNS S17400 | 17-4 Stainless | 18 |
UNS S34700 | 347 Stainless Steel | 18 |
UNS N08330 | 330 Stainless Steel | 19 |
UNS S66286 | Alloy A286 | 19 |
UNS S30400 | 304 Stainless Steel | 19 |
UNS S21800 | Nitronic® 60 | 19 |
UNS N08800 | Incoloy® 800 | 21 |
UNS S31600 | 316 Stainless Steel | 27 |
UNS S31000 | 310 Stainless Steel | 28 |
UNS N06230 | Haynes® 230 | 29 |
UNS N07718 | Inconel® Alloy 718 | 29 |
UNS N09925 | Incoloy® Alloy 925 | 31 |
UNS S20910 | Nitronic® 50 | 34 |
UNS N08904 | 904L Stainless Steel | 35 |
UNS S31803 | Duplex 2205 | 36 |
UNS S32550 | Ferralium® 255 | 40 |
UNS S32760 | Zeron® 100 | 41 |
UNS S32750 | Super Duplex 2507 | 43 |
UNS N08367 | AL6XN® | 46 |
UNS N06030 | Hastelloy® G30 | 48 |
UNS N06625 | Inconel® 625 | 51 |
UNS N06002 | Hastelloy® X | 52 |
UNS N06022 | Hastelloy® C-22 | 65 |
UNS N10276 | Hastelloy® C-276 | 68 |
UNS N08020 | Alloy 20 | 73 |
Note that these Nickel Systems materials are those materials which are commonly used when PREN values are being considered.
Below is a table comparing nickel Systems’ austenitic stainless steel materials.
Nickel Systems’ duplex materials are designed to resist saltwater corrosion. Check out our PREN value comparison table and choose the right material for your specific application.
Not all high nickel alloys resist saltwater corrosion well. Check out our PREN value comparison table below and select the right high nickel alloy material for your application.
Unsure how austenitic and duplex stainless steel compares to high nickel alloy material? Below is a master graph showing all of Nickel Systems’ materials that can be considered using PREN. Choose the right material for your specific application.
Please note that these values are believed to be accurate. However, they are estimated as the ASTM UNS chemical composition offers ranges, not precise values. Each trademarked product may have a slightly different PREN depending on their precise chemical composition. Referencing this blog information should not be considered as a substitute for professional engineering consultation.
Whether you need a fastener with a moderate or high PREN value, Nickel Systems stocks it! Pick your desired material and fastener type and contact us today to receive a quote.
