What is HEDP Diphosphonic Acid CAS 2809-21-4?

HEDP Diphosphonic Acid is an organophosphonic acid with CAS 2809-21-4, EC 220-552-8, and molecular formula C2H8O7P2. It is also known as HEDP, etidronic acid, or 1-hydroxyethylidene-1,1-diphosphonic acid, and is commonly supplied as a water-soluble liquid solution or higher-purity solid.

What is HEDP mainly used for?

HEDP is mainly used as a scale inhibitor, corrosion inhibitor, and metal-ion chelating agent in industrial water treatment. Typical systems include circulating cooling water, boiler water, industrial cleaning, and detergent formulations where calcium, magnesium, iron, or other metal salt deposition must be controlled.

Why does HEDP control scale and corrosion?

HEDP contains phosphonic acid groups that can sequester metal ions and adsorb onto surfaces, helping to prevent insoluble scale formation and reduce corrosion. This makes it useful in hardness-containing water systems where inorganic deposits or metal contamination would otherwise reduce efficiency or damage equipment.

What should be confirmed about the supplied grade?

Confirm active content or concentration, appearance, pH, density, phosphorus content or assay, chloride and iron content where relevant, and color. Liquid and solid grades differ in active content and handling, so the required supply form and concentration should be specified for the target formulation.

How should HEDP Diphosphonic Acid be stored and handled?

Store it in tightly closed original containers in a cool, dry, well-ventilated area away from direct sunlight, excessive heat, strong oxidizers, and incompatible materials. Use appropriate PPE and avoid skin or eye contact, especially when handling acidic liquid solutions.

HEDP Diphosphonic Acid CAS 2809-21-4

HEDP Diphosphonic Acid is an organophosphonic acid water treatment chemical widely used in formulations that require scale inhibition, corrosion control, and metal ion chelation. It is commonly applied in circulating cooling water systems, boiler water treatment, industrial cleaning systems, and related process water applications. Amino Trimethylene Phosphonic Acid is a related phosphonate scale inhibitor used in treatment-program selection. In supplier-side product positioning, HEDP is better presented as a functional water treatment chemical rather than as a chemical intermediate. Standard export supply can be arranged with routine documentation such as COA, TDS, and SDS according to customer requirements.

CAS: 2809-21-4
Synonyms: HEDP; 1-Hydroxyethylidene-1,1-Diphosphonic Acid; Etidronic Acid
Einecs: 220-552-8
Molecular Formula: C2H8O7P2
Grade: Industrial grade / water treatment grade
Package: Available in standard export packaging according to concentration, supply form, and order quantity.

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Product Description

1 Physicochemical Properties

2 Typical Applications

3 Product Function

4 Typical Supply Form

5 Packaging

6 Storage

Physicochemical Properties

Item	Description
Product Name	HEDP Diphosphonic Acid
CAS No.	2809-21-4
Synonyms	HEDP; 1-Hydroxyethylidene-1,1-Diphosphonic Acid; Etidronic Acid
EC No.	220-552-8
Molecular Formula	C2H8O7P2
Molecular Weight	206.03 g/mol
Appearance	Usually supplied as a colorless to pale yellow transparent liquid solution; solid or higher-purity forms may also be available depending on grade.
Solubility	Soluble in water.
Chemical Type	Organophosphonic acid / chelating agent / scale inhibitor
Main Functional Features	Scale inhibition, corrosion inhibition, sequestration, and metal ion chelation.
Supply Form	Commonly offered as aqueous solution for industrial use; exact concentration depends on supplier specification.

Typical Applications

Industrial water treatment formulations for scale and corrosion control.
Circulating cooling water systems.
Boiler water treatment systems.
Industrial cleaning and detergent formulations requiring metal ion control.
Process systems where calcium, magnesium, iron, or other metal salt deposition must be reduced.

Product Function

HEDP Diphosphonic Acid functions mainly as a scale inhibitor, corrosion inhibitor, and chelating agent. It helps control the formation of inorganic deposits and improves formulation stability in systems exposed to hardness ions and metal contaminants.

Typical Supply Form

This product is commonly supplied as an aqueous solution for water treatment and industrial formulation use. Exact active content, pH range, and other specification items may vary according to the required grade and supply standard. Detailed technical parameters can be provided in the TDS or supply specification upon request.

For related phosphonate water-treatment pages, compare HPAA, PBTC, and ATMP.

Packaging

HEDP Diphosphonic Acid is usually packed in sealed plastic drums, IBC totes, or other standard export containers suitable for liquid chemical transport. Packaging can be arranged according to concentration, shipment volume, and customer logistics requirements.

Storage

Store in a cool, dry, and well-ventilated place in tightly closed original containers. Protect the product from direct sunlight, excessive heat, and contamination during storage and transport. Keep container integrity intact to maintain stable supply quality.

FAQ - Technical & Supply Chain

Q:
What is HEDP Diphosphonic Acid CAS 2809-21-4?

A: HEDP Diphosphonic Acid is an organophosphonic acid with CAS 2809-21-4, EC 220-552-8, and molecular formula C2H8O7P2. It is also known as HEDP, etidronic acid, or 1-hydroxyethylidene-1,1-diphosphonic acid, and is commonly supplied as a water-soluble liquid solution or higher-purity solid.
Q:
What is HEDP mainly used for?

A: HEDP is mainly used as a scale inhibitor, corrosion inhibitor, and metal-ion chelating agent in industrial water treatment. Typical systems include circulating cooling water, boiler water, industrial cleaning, and detergent formulations where calcium, magnesium, iron, or other metal salt deposition must be controlled.
Q:
Why does HEDP control scale and corrosion?

A: HEDP contains phosphonic acid groups that can sequester metal ions and adsorb onto surfaces, helping to prevent insoluble scale formation and reduce corrosion. This makes it useful in hardness-containing water systems where inorganic deposits or metal contamination would otherwise reduce efficiency or damage equipment.
Q:
What should be confirmed about the supplied grade?

A: Confirm active content or concentration, appearance, pH, density, phosphorus content or assay, chloride and iron content where relevant, and color. Liquid and solid grades differ in active content and handling, so the required supply form and concentration should be specified for the target formulation.
Q:
How should HEDP Diphosphonic Acid be stored and handled?

A: Store it in tightly closed original containers in a cool, dry, well-ventilated area away from direct sunlight, excessive heat, strong oxidizers, and incompatible materials. Use appropriate PPE and avoid skin or eye contact, especially when handling acidic liquid solutions.

Ordering & Documentation

Key information for document requests, quotations, and supply planning.

Documents

COA, TDS, SDS/MSDS and packing details are available on request.

Quotation

Send the CAS number, grade, quantity, packing preference and destination.

Sample & Supply

Support is available for samples, trial orders, bulk and repeat supply.

Storage & Shipping

Product-specific conditions are confirmed before order.

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