Hydroxyethylidene diphosphonic acid (HEDP) is an organophosphoric acid corrosion inhibitor. It can chelate with Fe, Cu, and Zn ions to form stable chelating compounds. HEDP can dissolve the oxidized materials on these metals’ surfaces.

HEDP shows the excellent scale and corrosion inhibition effects under temperatures 2℃. It has good chemical stability under high pH values, is hard to be hydrolyzed, and is hard to be decomposed under ordinary light and heat conditions. Its acid/alkali and chlorine oxidation tolerance are better than other organophosphoric acids (salt).

HEDP can react with metal ions in the water system to form a hexa-element chelating complex, particularly calcium ions. Therefore, hydroxy ethylidene diphosphonic acid has good antiscale and visible threshold effects. In addition, when built together with other water treatment chemicals, it shows good synergistic effects.

The solid-state of HEDP is crystal powder, suitable for usage in winter and freezing districts. In addition, because of its high purity, it can be used as a cleaning agent in electronic fields and as an additive in daily chemicals.

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Molecular Formula:


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Structure Formula:

HEDP structure formula


AppearanceClear, Colorless to pale yellow aqueous solutionWhite crystal powder
Active content (HEDP), %58.0-62.090.0 Min.
Phosphorous acid (as PO33-), %1.0 Max.0.8 Max.
Phosphoric acid (as PO43-), %0.6 Max.0.5 Max.
Chloride (as Cl), ppm100.0 Max.50.0 Max.
pH (1% solution)2.0 Max.2.0 Max.
Density (20°C), g/cm31.43-1.47
Fe, mg/L10.0 Max.5.0 Max.
Color APHA, Hazen30.0 Max.


Hydroxyethylidene diphosphonic acid (HEDP) is used as scale and corrosion inhibition in circulating cool water systems, oil fields, and low-pressure boilers in fields such as electric power, chemical industry, metallurgy, fertilizer, etc.

In the light woven industry, HEDP is used as a detergent for metal and nonmetal. In addition, HEDP is used as a peroxide stabilizer and dye-fixing agent in the dyeing industry.

In non-cyanide electroplating, HEDP is used as a chelating agent. The dosage of 1-10mg/l is preferred as a scale inhibitor, 10-50mg/l as a corrosion inhibitor, and 1000-2000mg/l as a detergent. Usually, HEDP is used together with polycarboxylic acid.

Packing and Storage:

HEDP liquid: 200L plastic drum, IBC(1000L), customers’ requirement.

200l plastic drum 1000l IBC

HEDP solid: 25kg/bag, customers’ requirement.

25kg paper bags

Storage for ten months in a shady and dry place.

Safety Protection:

Acidity, Avoid contact with eye and skin. Once contacted, flush with water.


Dequest 2010, Etidronic acid, 1-Hydroxy Ethylidene-1 1-Diphosphonic Acid.


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