🔹 Types of Stainless Steel in Pharmaceuticals

1. SS 304 / 304L (AISI 304)

• Composition: 18% Cr, 8% Ni

• 304L = low carbon version → better weldability, less sensitization

• Applications:

  • Non-contact parts (frames, supports, furniture, piping for non-critical utilities)

  • Storage tanks for non-corrosive materials

  • Equipment housings, cleanroom furniture

• Limitations: Susceptible to chloride stress corrosion (pitting, crevice corrosion).

2. SS 316 / 316L (AISI 316)

• Composition: 16–18% Cr, 10–14% Ni, 2–3% Mo

• 316L = low carbon → superior resistance to corrosion after welding

• Applications:

  • Contact parts of manufacturing equipment (reactors, blenders, coating pans, fluid bed dryers)

  • Water systems (PW, WFI, clean steam lines)

  • Pipelines, tanks, filling machines

• Reason: Molybdenum improves resistance to chlorides and chemical attack.

• Industry Standard: Most common for pharma contact surfaces.

3. SS 904L

• Composition: High Ni (~23–28%), Mo (~4–5%), Cu addition

• Applications:

  • Highly corrosive environments (high chloride content, aggressive acids)

  • WFI distribution systems in tropical/high humidity regions

  • Used where 316L is inadequate

• Limitations: Expensive, more difficult to machine/weld.

4. Duplex Stainless Steels (e.g., 2205, 2507)

• Microstructure: Mix of austenite + ferrite

• Strength: Higher mechanical strength, better stress corrosion resistance than 316L

• Applications:

  • Some pharma water systems where high chloride levels are expected

  • Special cases where strong resistance to cracking and higher strength is required

• Limitations: Less common in pharma due to fabrication difficulties.

5. Other Special Grades

• SS 317L: Higher Mo than 316L; used rarely for stronger chemical resistance

• SS 410 / 420 (Martensitic): High hardness → used for scissors, blades, surgical instruments

• SS 440: Very hard, used for surgical cutting tools

• SS 321 / 347: Stabilized with Ti/Nb; used in high-temperature applications (steam systems, heat exchangers)

🔹 Key Selection Considerations in Pharma

• Product contact vs non-contact: Use 316L for contact parts, 304L/other grades for non-contact.

• Corrosion resistance: Select higher grades (904L, Duplex) if chloride-rich or aggressive environment.

• Weldability & surface finish: Must allow electropolishing, passivation, and smooth Ra ≤ 0.4 µm for hygienic design.

• Regulatory compliance: Must meet ASME BPE, ASTM, and GMP requirements.

✅ Summary Table

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