What drugs can DTPMPA be combined with?

Diethylenetriamine penta(methylene phosphonic acid) (DTPMPA or DTPMP) is a highly effective phosphonic acid-based scale and corrosion inhibitor. Due to its h3 chelating ability, thermal stability, and tolerance to high pH, it is often combined with other water treatment chemicals to enhance performance. Below are the key drug/chemical combinations and their applications:

1. DTPMPA + Corrosion Inhibitors

(1) Zinc Salts (Zn²⁺)

Synergy: Forms a protective film on metal surfaces (Fe, Cu).

Application: Cooling water systems (pH 6–9).

Ratio: DTPMPA (10–20 mg/L) + Zn²⁺ (1–5 mg/L).

(2) Molybdate (MoO₄²⁻)

Benefit: Non-toxic, environmentally friendly corrosion inhibition.

Use Case: Closed-loop systems, potable water.

Dosage: DTPMPA (15 mg/L) + MoO₄²⁻ (10 mg/L).

(3) Organic Azoles (BTA/TTA)

Target: Prevents copper corrosion in heat exchangers.

Ratio: DTPMPA (5–10 mg/L) + Benzotriazole (BTA, 1–3 mg/L).

2. DTPMPA + Scale Inhibitors

(1) Polyacrylic Acid (PAA) / Polymaleic Acid (HPMA)

Function: Enhances dispersion of CaCO₃, Ca₃(PO₄)₂.

Application: RO systems, boiler water.

Dosage: DTPMPA (5–15 mg/L) + PAA (2–10 mg/L).

(2) Phosphonates (HEDP/ATMP)

Synergy: Broad-spectrum scale inhibition (Ca, Ba, Sr scales).

Use Case: Oilfield injection water.

Ratio: DTPMPA + HEDP (1:1 blend, 10–30 mg/L total).

3. DTPMPA + Biocides

(1) Oxidizing Biocides (NaClO, ClO₂)

Challenge: DTPMPA is oxidant-resistant but may degrade at high Cl₂ doses.

Solution: Use low chlorine (<1 mg/L) + DTPMPA (10–20 mg/L).

(2) Non-Oxidizing Biocides (Isothiazolinones, Glutaraldehyde)

Benefit: Controls biofilm without affecting DTPMPA stability.

Example: DTPMPA (15 mg/L) + DBNPA (5–10 mg/L).

4. DTPMPA + Surfactants (For Cleaning & Dispersancy)

Purpose: Improves penetration into existing scales/biofilms.

Combination: DTPMPA + Nonionic surfactants (e.g., Triton X-100).

Use: Pre-cleaning of heat exchangers.

5. DTPMPA + Alkalis (For High-pH Systems)

NaOH/KOH: Maintains solubility in alkaline boilers (pH 10–12).

Dosage: DTPMPA (5–20 mg/L) + NaOH (to adjust pH).

6. Industrial-Specific Blends

Industry Recommended Combination Purpose

Oil & Gas DTPMPA + HEDP + Zn²⁺ Scale/corrosion inhibition

Power Plants DTPMPA + MoO₄²⁻ + BTA High-temp boiler protection

Cooling Towers DTPMPA + PAA + Isothiazolinone Scale + microbial control

RO Desalination DTPMPA + SHMP (sodium hexametaphosphate) Antiscalant for membranes

7. Incompatible Combinations

High-dose Fe³⁺/Al³⁺: May form insoluble precipitates.

High-sulfate waters: Can reduce efficacy of phosphonates.

Conclusion

DTPMPA works best when combined with:

✅ Corrosion inhibitors (Zn²⁺, MoO₄²⁻, BTA)

✅ Scale inhibitors (PAA, HEDP)

✅ Biocides (isothiazolinones, DBNPA)

✅ Surfactants (for cleaning applications)

Optimal performance depends on:

Water chemistry (pH, hardness, TDS).

System temperature.

Compatibility testing before full-scale application.