etidronic acid; HEDP
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Etidronic acid, HEDP

Etidronic acid;
HydroxyEthylidene DiPhosphonic acid;

CAS No.: 2809-21-4;
EC Number: 220-552-8;
EC Name: Etidronic acid;
Molecular formula: C2H8O7P2
Relative molecular mass: 206.03

Hydroxyethylenebisphosphonic acid; HEDPA;
IUPAC Name: (1-hydroxyethane-1,1-diyl)bis(phosphonic acid)

HEDP (Etidronic acid) is a typical organophosphine chelating agent, as water treatment scale and corrosion inhibitor, cleaning and descaling agent, sequestering and complexing agent, etc.

HEDP complexes calcium and magnesium ions in hard water to form soluble metal complexes, as water treatment scale and corrosion inhibitor, cleaning agent.
HEDP complexes iron, copper, zinc and other metal ions, as metal ion chelating agent, used in daily chemical and industrial cleaners, detergent formulations, paper pulp, textile printing and dyeing auxiliaries, metal surface treatment, etc.

We provide HEDP 60% liquid and 90% solid now.
Etidronic acid powder (crystal solid) can be used in cosmetics, winter cold envirenment, etc. And powder form products are usually more cost effective than liquid products in package and shipment fee.

Technical Data

AbbreviationHEDP LiquidHEDP Solid
AppearanceColorless to pale yellow transparant liquidWhite crystalline powder
Active content (as HEDP)60% min.90% min.
Phosphoric acid, as PO43-0.8% max.0.5% max.
Phosphorous Acid, as PO33-2.0% max.0.8% max.
chloride, as Cl250 μg/g (ppm) max.100 ppm max.
pH, 10g/L, 1% water solution2.0 max.2.0 max.
Density, 20℃1.4 g/cm3
Iron, as Fe20 ppm max.10 ppm max.
Chelation value, mg CaCO3 /g HEDP500 min.
HEDP Acid, CAS No.: 2809-21-4

We supply HEDP salts too, e.g. CAS RN: 29329-71-3 (HEDP.x-Na), 3794-83-0 (HEDP.4-Na)

Features of HEDP

  1. high temperature, acid and alkali resistance, can be used for water treatment scale inhibitor, corrosion inhibitor, descaling agent, cleaning agent, complexing agent, etc..
    HEDP is stable at high temperature and high pH value, good scale inhibition at 200℃, decomposition above 250℃, acid and alkali resistant.
  2. HEDP and iron, copper, magnesium, aluminum, zinc and other metals to form a stable water-soluble chelate.
    HEDP can form a six-ring chelate with metal ions in water, especially calcium ions, with a good scale inhibition effect, and there is an obvious threshold effect (also known as the solubility limit effect, after the use of a critical point, scale inhibition effect can be non-linearly increased significantly).
  3. HEDP and other water treatment agent compound use, showing the ideal synergistic effect.
    HEDP can be used with hydroxyacetic acid, PAA, BTA, molybdate, copolymer, zinc salt, etc., compound organic alkaline water treatment agent or low phosphorus zinc-based water treatment agent, can be used in a variety of different water quality of circulating cooling water system.
    HEDP is mainly used as industrial circulating cooling water, oilfield injection and boiler water treatment with molybdate, silicate, zinc salt and copolymer compound, corrosion inhibition, scale inhibition.


HEDP is generally used as scale inhibitor with concentration of 1-10mg/L;
As corrosion inhibitor with concentration of 10-50mg/L;
As cleaning agent with concentration of 1000-2000mg/L;

Scale inhibition and corrosion inhibition: widely used in industrial circulating cooling water systems, low and medium pressure boilers, oilfield water injection and oil pipeline. HEDP is usually used with polycarboxylic acid type scale inhibitor and dispersant.
Cleaning agent & detergent: hard surface cleaning, cleaners for metal and non-metal materials, industrial cleaning agent, industry soap, metal ion chelating agent.
Textiles auxiliaries: peroxide stabilizer and color fixing agent in bleaching and dyeing;
Non-cyanide plating process, as a complexing agent, can dissolve metal surface oxides.

Related Products:
If you need stronger alkali resistance or non-phosphorus chelating agents / sequestrants, please feel free to consult us.

Traditonal Chelating Agents
Aminopolycarboxylates: EDTA acid, EDTA-Na/K, DTPA & DTPA-5Na/5K
Polyphosphonates: HEDP, DTPMP, ATMP

Package and storage:
25kg or 30kg per plastic drum;
125kg, or 250kg per plastic drum;
1250kg per IBC.
Store in a cool and ventilated place indoors, moisture-proof, storage period of 12 months.

Safety and protection
Acidic, should avoid contact with eyes and skin, once splashed, should be immediately flushed with plenty of water.

Supplier and Manufacturer

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