PREN / Pitting Resistance Equivalent
Calculates the Pitting Resistance Equivalent Number (PREN = Cr + 3.3×Mo + 16×N) from chromium, molybdenum, and nitrogen content, and compares it against the source's stated PREN > 40 pitting-resistance indication. This is an arithmetic index only — not a corrosion test, material approval, seawater approval, or fitness-for-service assessment.
Engineering calculator — results require technical review before production use.
Source & assumptions
IWE Module 2 – Materials and Their Behavior during Welding, Chapter 15, Section 3.3 (Duplex-Steel) and Chapter 14, Section 11.3 (Pitting)
Assumptions
- PREN = Cr + 3.3×Mo + 16×N — both the duplex-steel section (Ch. 15.3.3) and the pitting section (Ch. 14.11.3) give this identical formula.
- Cr, Mo, and N are entered as weight percent (wt%). PREN itself is a dimensionless pitting-resistance index, not a weight percent or any other kind of percentage — the source's threshold is stated as "PREN > 40", not "PREN > 40%".
- PREN is calculated arithmetically from the entered values — this calculator does not look up or infer composition from any grade or standard.
- The source states PREN > 40 as a pitting-resistance indication in the duplex/super-duplex context (Ch. 15.3.3) — reported here as a > 40 comparison, an indication only, never an approval decision.
- Results require engineering review before production use.
Limitations
- PREN is an index/indicator only — not a corrosion test.
- It does not account for heat treatment, welding heat input, shielding/backing gas quality, surface condition, oxide scale, crevices, deposits, chloride concentration, temperature, flow, fabrication quality, or service environment.
- It does not predict actual pitting performance.
- It does not approve material selection, and does not approve seawater service.
- It does not replace material specification review, corrosion engineering review, WPS/PQR, production testing, or engineering judgement.
- It does not implement Schaeffler, DeLong, or WRC diagrams, ferrite number, phase prediction, martensite prediction, cracking assessment, or hardness prediction, and does not classify grade beyond the source-stated PREN > 40 indication.
- The 'unusually high' per-element sanity-check warnings (Cr, Mo, N — reused from Cr/Ni Equivalent's thresholds) are implementation-level heuristics, not sourced from IWE Module 2 as compositional limits.