Can EDTMP.Na5 replace ATMP.Na4?

Yes, EDTMP•Na₅ can replace ATMP•Na₄ in many applications, but the suitability depends on specific requirements such as scale inhibition efficiency, corrosion protection, thermal stability, and environmental factors. Below is a detailed comparison and replacement analysis.

1. Key Differences Between EDTMP•Na₅ and ATMP•Na₄

Property EDTMP•Na₅ ATMP•Na₄

Chemical Structure Contains 4 phosphonate groups + N Contains 3 phosphonate groups + N

Chelating Ability Stronger (higher metal ion binding) Moderate

Scale Inhibition Better for CaSO₄, BaSO₄, SrSO₄ Better for CaCO₃

Corrosion Inhibition Stronger (forms stable metal films) Moderate (requires Zn²⁺ synergy)

Thermal Stability Stable up to 100°C Stable up to 80°C

pH Range Effective at pH 2–12 Effective at pH 2–9

Biodegradability Low (like ATMP) Low

Cost Higher (more complex synthesis) Lower

2. When Can EDTMP•Na₅ Replace ATMP•Na₄?

✅ Preferred Replacement Cases

(1) High-Sulfate Water (Oilfield, Seawater Cooling)

EDTMP•Na₅ is superior for BaSO₄/SrSO₄ inhibition, making it ideal for oilfield injection water where ATMP•Na₄ may fail.

Example: In offshore platforms, EDTMP prevents sulfate scaling in seawater-based systems.

(2) High-Temperature Systems (>80°C)

EDTMP•Na₅ remains stable up to 100°C, while ATMP•Na₄ degrades above 80°C.

Example: High-pressure boilers or geothermal applications.

(3) Stronger Corrosion Protection Needed

EDTMP•Na₅ forms more stable chelates with Fe³⁺, Cu²⁺, reducing pitting corrosion in carbon steel and copper alloys.

Example: Closed-loop cooling systems in power plants.

(4) Wider pH Range Applications

EDTMP•Na₅ works in h3ly alkaline (pH 12) or acidic (pH 2) conditions, unlike ATMP•Na₄ (best at pH 2–9).

Example: Metal pickling (acidic) or textile bleaching (alkaline).

❌ Cases Where ATMP•Na₄ is Still Preferred

(1) Cost-Sensitive Applications

ATMP•Na₄ is cheaper (~20–30% lower cost) and sufficient for low-hardness freshwater systems.

Example: Small-scale cooling towers with moderate scaling risk.

(2) Calcium Carbonate (CaCO₃) Dominant Scaling

ATMP•Na₄ is slightly better at inhibiting CaCO₃ in low-sulfate water.

Example: Municipal water treatment for drinking water systems.

(3) Where Phosphorus Discharge is Restricted

Both contain phosphorus, but ATMP•Na₄ has slightly lower P content (if regulatory limits are tight).

3. How to Switch from ATMP•Na₄ to EDTMP•Na₅?

Dosage Adjustment

EDTMP•Na₅ is typically more efficient; reduce dosage by 10–30% compared to ATMP•Na₄.

Example: If ATMP•Na₄ was dosed at 20 mg/L, EDTMP•Na₅ may work at 15 mg/L.

Compatibility Testing

Check for precipitation risks when mixed with other water treatment chemicals (e.g., Zn²⁺, polyacrylates).

Performance Monitoring

Test scale/corrosion rates after switching (e.g., using coupon tests or LSI/RSI indices).

4. Environmental & Safety Considerations

Both are non-biodegradable and contain phosphorus (regulated in some regions).

EDTMP•Na₅ has lower toxicity than ATMP•Na₄ for aquatic life (lower Zn²⁺ mobilization risk).

Final Recommendation

Replace ATMP•Na₄ with EDTMP•Na₅ if:

You deal with sulfate scales (BaSO₄, SrSO₄).

Operating high-temperature (>80°C) or wide pH range systems.

Need h3er corrosion inhibition.

Stick with ATMP•Na₄ if:

Cost is a major constraint.

Only CaCO₃ scaling is present.

Local regulations strictly limit phosphorus discharge.

For critical applications, conduct bench-scale testing before full replacement.