The grades
SS 304 — 18% Cr, 8% Ni. General-purpose austenitic stainless. Not ideal for WFI or product contact. SS 316 — adds 2-3% molybdenum for chloride pitting resistance. SS 316L — lower carbon (≤0.03%). Weldable without sensitisation. The pharma standard.
Why 316L for contact
1. Corrosion resistance — resists WFI, PW, and most APIs. 2. Weld integrity — low-C prevents carbide precipitation during welding, so no crevice corrosion. 3. Surface finish — polishable to Ra < 0.4 µm, meeting ASME BPE. 4. Regulatory alignment — FDA, EU-GMP, WHO-GMP all accept 316L for product-contact.
What to verify on a new machine
- Material test certificates (heat numbers traceable) - Surface roughness reports (< 0.5 µm internal, < 0.8 µm external) - Weld procedure and inspection records - Passivation certificate
Our commitment
Every Kailash Machine Tools machine ships with full material traceability.