Pitting Resistance Equivalent Number (PREN)
Engineering definition, metallurgical mechanisms, standard testing specifications, and manufacturing guidelines for closed-die forgings up to 50 kg.
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A standardized mathematical formula that rates the localized pitting and crevice corrosion resistance of stainless steels based on their Chromium, Molybdenum, and Nitrogen content.
Technical Explanation & Metallurgical Principles
The PREN formula quantitatively ranks an alloy's resistance to localized breakdown of the passive film in chloride-rich environments like ocean seawater, brine, and sour oil wells. Alloys with PREN ≥35 are classified as Duplex, while PREN ≥40 is required for Super Duplex offshore service.
Key Engineering Specifications & Parameters
| Technical Parameter / Metric | Engineering Benchmark / Value |
|---|---|
| Standard Formula | PREN = %Cr + 3.3(%Mo) + 16(%N) [or 30(%N) in some specs] |
| SS 316L Rating | PREN ~ 23 – 25 |
| Duplex 2205 Rating | PREN ≥ 35 (guaranteed) |
| Super Duplex 2507 Rating | PREN ≥ 42 (deepwater seawater qualified) |
Application at Jayesh Forge (Rajkot Plant)
Every heat of Duplex 2205 and Super Duplex 2507 forged at our Rajkot plant is certified with an actual calculated PREN recorded on the EN 10204 3.1 MTC.
Related Materials, Standards & Products
Engineered Product Lines
Related Metallurgical & Testing Terms
Duplex Stainless Steel (2205 / F51 / S31803)
A dual-phase stainless steel possessing an approximate 50% austenitic and 50% ferritic microstructure, combining twice the yield strength of 316L with supreme chloride pitting resistance.
Super Duplex Stainless Steel (2507 / F53 / S32750)
An ultra-high-alloyed 25% Chromium duplex stainless steel with PREN ≥ 42, engineered for deepwater offshore subsea manifolds and boiling seawater service.
Questions Regarding Pitting Resistance Equivalent Number (PREN)
Dissolved interstitial Nitrogen is roughly 16 times more potent than Chromium at preventing the initiation of pitting corrosion in chloride-bearing electrolytes.
Request a Forging Quote with Pitting Resistance Equivalent Number (PREN) Compliance
Our Rajkot metallurgy desk is ready to review your technical drawings, testing protocols, and delivery schedules for custom closed-die forgings strictly up to 50 kg.