EN 10253-2 Type B buttweld pipe fittings for pharmaceutical manufacturing — Water for Injection (WFI), purified water distribution, clean steam, API synthesis, and bioreactor utility piping. The critical distinction in pharma is delta ferrite control: 1.4435 (≤1 FN) for WFI and critical purity systems; 1.4404 (standard 316L) for general utility.
When 316L stainless steel solidifies, small islands of ferrite-phase steel (3–8 FN in standard 1.4404) are trapped in the austenite matrix. These are not a defect in normal service — but in ultra-pure water systems they create micro-galvanic cells at the ferrite/austenite interface.
In WFI and purified water at low-conductivity (0.1–1.2 µS/cm), micro-galvanic corrosion at ferrite pools produces sub-micron pits that harbour biofilm — a direct contamination risk. Regulators (FDA, EMA) and ISPE guidelines require ≤1 FN for WFI contact surfaces to eliminate this mechanism.
1.4435 (X2CrNiMo18-14-3) specifies Ni 12.5–15% — higher than 1.4404's 10–14% minimum. The elevated Ni fully shifts the austenite stability boundary, suppressing delta ferrite to ≤1 FN. Same PRE ~24, same corrosion resistance — only the solidification microstructure differs.
| System | Grade | W.Nr. | Certificate | Note |
|---|---|---|---|---|
| Water for Injection (WFI) loops | 316L Low-Ferrite | 1.4435 | EN 10204 3.2 (TÜV) | ≤1 FN mandatory for WFI contact |
| Purified Water (PW) distribution | 316L Low-Ferrite | 1.4435 | EN 10204 3.1 or 3.2 | ISPE recommends ≤1 FN |
| Clean steam (CS) generation/distribution | 316L | 1.4404 | EN 10204 3.1 | Steam contact — FN less critical |
| API synthesis — general solvent | 316L | 1.4404 | EN 10204 3.1 | Standard chemical resistance |
| API synthesis — halide/acidic solvent | 316L / Duplex | 1.4404 / 1.4462 | EN 10204 3.1 | Grade by chloride and temperature |
| Bioreactor utility (CIP/SIP) | 316L | 1.4404 | EN 10204 3.1 | NaOH/HNO₃ CIP compatible |
| Cooling water (utility grade) | 304L | 1.4307 | EN 10204 3.1 | Non-product-contact utility loops |
The WFI-qualified grade. Higher Ni suppresses delta ferrite to ≤1 FN — eliminates micro-galvanic pitting and biofilm harbour in ultra-pure water. EN 10204 3.2 (TÜV) typically required for IQ documentation.
Full grade page →Standard 316L for clean steam, API synthesis with general solvents, CIP/SIP utility, and non-WFI clean systems. Fully adequate where ultra-low ferrite is not specified.
Full grade page →304L for non-product-contact utility: plant cooling water, non-sterile HVAC, purge gas lines, secondary cooling circuits. Lower cost where Mo is not required.
Full grade page →EN 10204 3.1 standard. EN 10204 3.2 (TÜV Rheinland / TÜV SÜD) for WFI and IQ/OQ documentation. Delta ferrite test report (FN number per casting). Chemical & mechanical certificates with heat traceability. Surface finish Ra documentation (Ra ≤0.8 µm electropolished). PED 2014/68/EU Declaration of Conformity.
