HEDP·Na₄ is a widely used phosphonic acid-based scale and corrosion inhibitor with excellent chelating and threshold inhibition properties. Here are its key features and applications:
1. Key Characteristics
- Chemical Structure: Contains two phosphonate groups with high stability.
- Chelation Ability: Strong binding with Ca²⁺, Mg²⁺, Fe²⁺/³⁺, Cu²⁺ ions.
- Thermal Stability: Effective up to 100°C (better than many organic phosphonates).
- pH Range: Works well in pH 2–9 (acidic to neutral conditions).
- Low Dosage Effect: Exhibits “threshold effect” (effective at 1–10 mg/L).
2. Primary Applications
| Application | Dosage (mg/L) | Key Benefits |
|---|---|---|
| Cooling Water Systems | 5–20 | Controls scale + corrosion |
| Boiler Water | 3–15 | Prevents Ca₃(PO₄)₂ and Fe₂O₃ deposition |
| RO Systems | 2–8 | Inhibits CaCO₃ scaling on membranes |
| Industrial Cleaning | 100–500 (as cleaner component) | Removes metal oxide deposits |
3. Technical Advantages
- Scale Inhibition:
- Highly effective against CaCO₃, CaSO₄, and BaSO₄.
- Superior to polyphosphates (doesn’t hydrolyze into orthophosphate).
- Corrosion Control:
- Forms protective films on metal surfaces (Fe, Cu).
- Often combined with zinc ions for enhanced protection.
- Compatibility:
- Works well with chlorine (more stable than ATMP but less than PBTC).
- Synergistic with polymers (e.g., PAA, PAS) for dispersion.
4. Comparison with Other Phosphonates
| Property | HEDP·Na₄ | ATMP | PBTC |
|---|---|---|---|
| Oxidant Stability | Moderate | Poor | Excellent |
| Calcium Tolerance | High | Very High | High |
| pH Range | 2–9 | 1–9 | 6–10 |
| Cost | Moderate | Low | High |
Note: HEDP·Na₄ is often preferred for low-to-mid pH systems and iron-rich water.
5. Usage Guidelines
- Dosing Method:
- Continuous feed (recommended): Dilute to 5–10% solution.
- Batch treatment: For small systems or cleaning applications.
- Incompatibilities:
- ❌ Avoid high Fe³⁺/Al³⁺ concentrations (may precipitate).
- ❌ Don’t mix with strong acids/bases before dilution.
- Environmental Note:
- Biodegradability: Poor (requires monitoring of phosphorus discharge).
- Meets EPA and EU REACH standards at typical dosages.
6. Safety & Handling
- Storage: Keep in plastic containers; stable at ambient temperature.
- Protection: Wear gloves/goggles; avoid inhalation of dust.
- First Aid:
- Skin contact: Rinse with water for 15 minutes.
- Eye contact: Flush with water and seek medical help.
Why Choose HEDP·Na₄?
- Cost-Effective: Balances performance and price for general water treatment.
- Versatile: Suitable for cooling, boiler, and cleaning applications.
- Reliable: Proven long-term stability in industrial systems.
For optimal results, conduct water analysis to adjust dosage based on hardness, pH, and system conditions. In oxidant-heavy systems (e.g., chlorinated cooling towers), PBTC·Na₄ may be a better alternative.