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1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP)

CAS No. 2809-21-4 EINECS No. 220-552-8
Molecular Formula C2H8O7P2 Molecular Weight 206.02
Structural Formula

HEDP Structural Formula

Product Features

HEDP is an organophosphonate corrosion inhibitor. HEDP shows multifunctional properties that includes scale inhibition and corrosion inhibition. HEDP is noted for excellent CaCO3 inhibitor and water hardness stabilizer. HEDP is very good complexing agent for metal ions like Fe, Cu, and Zn.

HEDP can react with metal ions in water system to form hexa-element chelating complex, with calcium ion in particular. When built together with other water treatment chemicals, HEDP shows good synergistic effects. HEDP shows excellent stability under high pH value, hard to be hydrolyzed, and hard to be decomposed under ordinary light and heat conditions. HEDP shows excellent scale and corrosion inhibition effects under temperature 250℃. HEDP acid/alkali and chlorine oxidation tolerance are better than that of other organophosphonate (salts).

HEDP can dissolve the oxidized materials on these metals’ surfaces.

HEDP solid form is a white crystalline powder with a melting point of 198-200°C, suitable for usage in winter and freezing districts. Highly soluble in water, acids, alkalis, methanol and ethanol. Because of its high purity, it can be used as cleaning agent in electronic fields and as additives in daily chemicals.

Technical Specification

Parameter Standard
Liquid Liquid
Appearance Clear, colorless to pale yellow aqueous solution White crystal powder
Active content(HEDP), % 58-62 90.0 min
Active content (HEDP·H2O), % - 98.0 min
Phosphorous acid (as PO33-), % 2.0 max 0.8 max
Phosphoric acid (as PO43-), % 0.8 max 0.5 max
Chloride (as Cl-), ppm 100.0 max 100.0 max
pH (1% water solution) 2.0 max 2.0 max
Density (20℃), g/cm3 1.43-1.47 -
Fe, mg/L 20.0 max 10.0 max
Color APHA (Hazen) 40.0 max -
Ca Sequestration (mg CaCO3/g) 500.0 min -

Applications & Usage

HEDP is widely used in several end use applications such as detergents (as chelant), industrial and institutional cleaners, personal care products, water treatment circulating cooling water systems, low-pressure boilers, swimming pool stain prevention, metal ion control, oilfield, textile, paper, peroxide stabilizer, electroplating, HEDP also can be used for formulating RO membrane antiscalants, thermal desalination antiscalants, formulation for treating sterilizers etc.

In light woven industry, HEDP is used as detergent for metal and nonmetal. In dyeing industry, HEDP is used as peroxide stabilizer and dye-fixing agent. In non-cyanide electroplating, HEDP is used as chelating agent.

Scale & Corrosion Inhibition Performance

CaCO3 inhibition CaSO4 inhibition Ca3(PO4)2 inhibition BaSO4 inhibition CaF2 inhibition
Excellent Poor Very Good Good Good
Calcium Tolerance Iron Control Sequestration Steel Corrosion inhibition
Poor Yes Good Very Good

Package & Storage

HEDP Liquid HEDP Solid
25L Drum 200L Drum 1000L IBC ISO Tank 25kg Bag Bulk Bag
25kg Bag 200L Drum packaging 1000L IBC packaging
Storage for 10 months in shady room and dry place.

Hazard & Safety Precaution

Hazard Information Safety Precaution

Corrosive, Class 8, UN 3265 Corrosive, Class 8, UN 3265

Wear protective gloves Wear protective goggles Wear protective clothing

Once contacted with eye and skin, flush with plenty of clean water.

Alternative Name / Synonyms

  1. HEDPA;
  2. Etidronic Acid;
  3. 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid;
  4. Hydroxyethylidene-1,1-diphosphonicacid(HEDP);
  5. 1-Hydroxyethylidenediphosphonic Acid;
  6. 1-Hydroxy-1,1-Ethanediyl ester;
  7. Oxyethylidenediphosphonic Acid(OEDP)

HEDP Salts

  1. Disodium Salt of 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP.Na2)
  2. Tetra Sodium Salt of 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP.Na4)
  3. Tetra Sodium of 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP.Na4 Granule)
  4. Potassium salt of 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP.K2)