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HEDP

HEDP (Hydroxyethylidene diphosphonic acid) is an organic phosphonic acid-based scale and corrosion inhibitor that forms stable complexes with various metal ions, such as iron, copper, and zinc, and dissolves oxides on metal surfaces.

It remains effective in preventing corrosion and scale formation even at 250°C, remains stable at high pH levels, and is resistant to hydrolysis. HEDP exhibits better resistance to acids, alkalis, and chlorine oxidation than other organic phosphonic acids (and their salts).


Applications

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Chemical Information

Item

Specification

CAS No.

2809-21-4

Molecular Formula

C₂H₈O₇P₂

Molecular Weight

206.03

Appearance

Colorless or pale yellow transparent liquid Powdery

crystalline solid

Odor

Odorless

Active Ingredient (as HEDP) % ≥

50.0

60.0

90

Phosphorous acid (as PO₃³⁻) % ≤

2.0

2.0

0.8

Phosphoric acid (as PO₄³⁻) % ≤

0.8

0.8

0.5

Chlorides (as Cl⁻) % ≤

0.01

0.01

0.01

pH (1% aqueous solution) ≤

2

2

1.5–2.0

Density (20°C) g/cm³ ≥

1.34

1.40

——

Calcium chelating value mg/g ≥

450

500

——

Iron ions ppm ≤

20

20

10

Advantages

● Widely used in industrial applications

● Demonstrates excellent stability even in the presence of chlorine gas

● Exhibits good corrosion inhibition properties even in the presence of zinc and other phosphates

● Performs stably at high temperatures and high pH levels

● Compared to other organic phosphonic acids (and salts), it offers superior resistance to acids, alkalis, and chlorine oxidation.

● HEDP reacts with metal ions in water to form hexavalent chelates. Consequently, HEDP exhibits excellent scale inhibition and a visible threshold effect.

● HEDP demonstrates good synergistic effects when used in combination with other water treatment chemicals.

● Due to its high purity in solid form, HEDP is suitable for use in winter and in extremely cold regions.

Applications

Liquid:

● Treatment of industrial circulating cooling water: HEDP effectively prevents scale formation, protecting industrial circulating cooling water systems from scale and corrosion. It forms stable complexes with various metal ions, including iron, copper, aluminum, and zinc, making it suitable for removing rust and inorganic salt deposits from boilers and pipes.

● Boiler and Heat Exchanger Protection: As a scale inhibitor and corrosion inhibitor, HEDP is used to protect boilers and heat exchangers by preventing internal scaling and corrosion, thereby extending equipment service life.

● Complexing Agent for Cyanide-Free Electroplating: In the electroplating industry, HEDP serves as a complexing agent for cyanide-free electroplating, enhancing plating efficiency and product quality.

● Cleaning Agent for Metals and Non-Metals: HEDP can be used as a cleaning agent for both metals and non-metals, removing dirt and impurities from the surfaces of various materials.

● Stabilizer and Fixative in the Dyeing Industry: In the dyeing industry, HEDP serves as a peroxide stabilizer and fixative, improving product quality and stability.

Solid:

● Additive for Household Chemicals: Due to its high purity, HEDP can also be used as an additive in household chemicals, such as cosmetics and detergents, to provide a better user experience.

● Cleaning agents in the electronics industry: In the electronics industry, HEDP is used to clean precision parts and equipment, improving equipment efficiency and stability.

● Carrier agents in the medical and healthcare sector: HEDP serves as a carrier for radioactive elements and is widely used in the diagnosis and treatment of thyroid and kidney diseases.

As a scale inhibitor, HEDP is typically used at concentrations of 1–10 mg/L; as a corrosion inhibitor, at 10–50 mg/L; and as a cleaning agent, at 1,000–2,000 mg/L. It is usually used in combination with polycarboxylic acid-based scale inhibitors and dispersants.

Packaging and Storage:

 Liquid HEDP is packaged in plastic drums, each containing 30 kg or 250 kg;

solid HEDP is packaged in plastic woven bags lined with polyethylene, with a net weight of 25 kg per bag, though packaging can be customized according to customer requirements.

Store in a cool, well-ventilated indoor area, protected from moisture.

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Safety and Protection:

HEDP is acidic; avoid contact with eyes and skin. If splashed onto the body, rinse immediately with plenty of water.

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