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)

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

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 detergent / detergent formulations, paper pulp, textile printing and dyeing auxiliaries, metal surface treatment, etc.

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

If you need stronger alkali resistance or non-phosphorus chelating agent, please feel free to consult us.

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

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.


Widely used in industrial circulating cooling water systems and low and medium pressure boilers;
Scale inhibition and corrosion inhibition of oilfield water injection and oil pipeline;
Cleaning agent for metal and non-metal materials, industrial cleaning agent;
In the daily chemical industry soap, detergent as metal ion chelating agent;
In textile printing and dyeing, peroxide stabilizer and color fixing agent in bleaching and dyeing;
In the non-cyanide plating process, as a complexing agent, can dissolve metal surface oxides.

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; usually used with polycarboxylic acid type scale inhibitor and dispersant.

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.

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