Valves for Sodium Hypochlorite (NaOCl — Bleach) Service
Sodium hypochlorite (NaOCl) is used as a disinfectant and bleaching agent in water treatment (typically 0.5–2 mg/L dosing), swimming pools, pulp bleaching (10–15% solution), and textile bleaching. Concentrated NaOCl (>10%) is highly corrosive and a strong oxidiser, attacking most metals. Even dilute hypochlorite causes pitting corrosion on SS 304 and attacks carbon steel rapidly. Valve materials must be carefully selected to avoid metal ion contamination and premature failure.
Pressure Range
1–10 barg (dosing and distribution)
Temperature
Ambient (max 25°C for storage stability)
Industries
Water treatment & disinfection, Swimming pools, Pulp & paper bleaching
Key Properties — Sodium Hypochlorite (NaOCl — Bleach)
- Strong oxidiser — highly corrosive to most common metals including CS and SS 304
- 10–15% NaOCl solution pH ~11–13: alkaline but corrosive due to hypochlorite ion
- Decomposes on heating and in sunlight — maximum storage temperature 25°C
- Active chlorine content degrades over time — fresh solution most aggressive
- Releases Cl₂ gas when acidified — HVAC hazard in enclosed pump rooms
Material Compatibility — Sodium Hypochlorite (NaOCl — Bleach)
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 |
|---|---|---|
| SS 316L | Fair | Acceptable for dilute (<1%) service only. Not for concentrated hypochlorite. |
| Hastelloy C-276 | Excellent | Best metallic choice for concentrated NaOCl. |
| Titanium Gr 2 | Excellent | Excellent resistance to hypochlorite. |
| PVDF-lined | Excellent | Best plastic-lined option for all NaOCl concentrations. |
| Carbon Steel | Not Recommended | Rapidly corroded by any NaOCl concentration. |
| Bronze / Brass | Not Recommended | Copper is oxidised by hypochlorite — releases Cu ions contaminating treated water. |
Recommended Valves
PVDF-lined Butterfly Valve
Most cost-effective large-bore isolation for concentrated NaOCl in water treatment and pulp bleaching
PVDF-lined Ball Valve
Small-to-medium bore isolation for NaOCl dosing systems
Diaphragm Valve (PVDF or PP body, PTFE diaphragm)
Accurate dosing control of hypochlorite — zero metal contact, no dead legs
Hastelloy C-276 Globe Valve
Control service where metallic valve is required for high-pressure hypochlorite
Valves to Avoid
Carbon steel valves
Bronze or brass valves — copper contamination
SS 316 for concentrated NaOCl
Special Considerations
Applicable Standards
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