MEDIA GUIDE
Caustic Soda Valves (NaOH)
Caustic embrittlement, not corrosion rate, is the binding constraint.
Stainless steels good to ~80°C (316L preferred over 304 — sensitization in welds is the weak link); above that caustic stress-corrosion cracking risk rises sharply — nickel alloys (Monel) or PTFE at high temperature.
Materials at a glance
| Material | Rating | Up to |
|---|---|---|
| Carbon steel (ASTM A216 WCB) | Good | 50 °C |
| Stainless steel 304 (ASTM A351 CF8) | Good | 70 °C |
| Stainless steel 316 (ASTM A351 CF8M) | Excellent | 80 °C |
| Monel 400 (ASTM A494 M35-1) | Excellent | 120 °C |
| Hastelloy C-276 (ASTM A494 CW6M) | Excellent | 120 °C |
| PTFE/PFA-lined ductile iron | Excellent | 150 °C |
Ratings: Excellent / Good / Conditional / Not recommended, from this site's boundary-and-medium data set. The manufacturer's data sheet for the specific product governs.
What drives the choice
- Carbon steel is standard at moderate concentration and temperature; nickel alloys above the caustic-embrittlement line
- The temperature–concentration combination is what matters — state both
- PTFE-lined valves are common in chemical-grade service
Where the boundaries sit
- Hot, concentrated caustic is a nickel-alloy duty — the chart's ceiling, not the valve's, decides
Related reading
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