Valves for Caustic Potash (KOH — Potassium Hydroxide) Service
Potassium hydroxide (caustic potash, KOH) is a strong alkaline chemical used in potassium soap production, fertilisers, batteries (alkaline and nickel metal hydride), electrolysers for green hydrogen production, and as a pH adjuster. It is handled in concentrations of 10–50% aqueous solution and is highly corrosive to skin and eyes. Unlike caustic soda (NaOH), KOH is slightly more corrosive to stainless steel at elevated concentration, but both behave similarly from a valve selection standpoint.
Pressure Range
1–20 barg
Temperature
Ambient to +120°C
Industries
Green hydrogen electrolysers, Potassium soap production, Fertiliser plants
Key Properties — Caustic Potash (KOH — Potassium Hydroxide)
- Strong alkali — pH >13 in solution; severely corrosive to skin and eyes
- Concentrated KOH attacks zinc, aluminium, and tin, and is aggressive to SS at high temp
- Compatible with carbon steel, SS 316L, Hastelloy, PTFE, PVDF
- Deliquescent solid — absorbs moisture from air; aqueous solutions are most common
- Heated KOH (>80°C) is more corrosive — stress corrosion cracking risk for carbon steel
Material Compatibility — Caustic Potash (KOH — Potassium Hydroxide)
Ratings are indicative. Actual compatibility depends on concentration, temperature, velocity, and presence of contaminants. Always consult corrosion tables or a materials engineer.
| Material | Rating | Notes |
|---|---|---|
| Carbon Steel (WCB) | Good | Acceptable for KOH <50% up to 80°C. SCC risk above 80°C for stressed CS. |
| SS 316L | Good | Good for dilute KOH; some SCC risk with concentrated hot KOH. |
| Hastelloy C-276 | Excellent | Excellent across all KOH concentrations and temperatures. |
| PTFE-lined / PVDF-lined | Excellent | Best for concentrated KOH — no metal contact. |
| Nickel 200 | Excellent | Nickel 200 is excellent for hot, concentrated KOH. |
| Aluminium | Not Recommended | Rapidly dissolved by KOH. |
Recommended Valves
Ball Valve (SS 316L or PTFE-lined)
Standard isolation for KOH dilution and distribution pipelines
PTFE-lined Butterfly Valve
Large-bore KOH service — cost-effective corrosion protection
Globe Valve (SS 316L, Hastelloy trim)
Throttling and control of KOH flow in electrolyser and soap plants
Diaphragm Valve (PTFE diaphragm)
Accurate KOH dosing control — no metal-fluid contact, zero leak path
Valves to Avoid
Aluminium or zinc-lined valves
Unlined carbon steel for hot concentrated KOH
Special Considerations
Applicable Standards
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