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Water Treatment Scale Corrosion Inhibitor CAS 2809-21-4 HEDP

Hydroxyethylidene diphosphonic acid (HEDP) is a new type of chlorine-free electroplating complexing agent. It is used as the main agent for stable water quality in the circulating cooling water system, and plays the role of corrosion and scale inhibition. This product is one of the organic polyphosphonic acid-free water tablet conditioners.
  • HEDP 60%


  • 3808940090

1-Hydroxy Ethylidene-1,1-Diphosphonic Acid(HEDP)

CAS No.   2809-21-4

Molecular Formula:   C2H8O7P2                                                                                         

Molecular weight:  206.02

Hazard class/UN No./Packaging: UN 3265 8/PG III

Structural Formula: 



HEDP is an organophosphoric acid corrosion inhibitor. It can chelate with Fe, Cu, and Zn ions to form stable chelating compounds.It can dissolve the oxidized materials on these metals’ surfaces. HEDP shows excellent scale and corrosion inhibition effects under temperature 250℃. HEDP has good chemical stability under high pH value, hard to be hydrolyzed, and hard to be decomposed under ordinary light and heat conditions. Its acid/alkali and chlorine oxidation tolerance are better than that of other organophosphoric acids (salt). HEDP can react with metal ions in water system to form hexa-element chelating complex, with calcium ion in particular. Therefore, HEDP has good antiscale and visible threshold effects. When built together with other water treatment chemicals, it shows good synergistic effects.


Item  Standard 

Clear colorless to pale tan liquid, free from

foreign matter

Active Acid % 60.0 min

Phosphorous acid as PO33- %

2.0 max

Phosphoric acid as PO43 %

0.8 max
Chloride as Cl  ppm 100 max

Sequestrant value (CaCO3) mg/g as

product at PH 11-12

500 min
PH (1% solution) @20 °C 2.0 max
Density (20℃),g/cm3
1.440 min
Iron content (Fe ppm) 35.0 max
Colour (Hazen) 80 max


HEDP is used as scale and corrosion inhibition in circulating cool water system, oil field and low-pressure boilers in fields such as electric power, chemical industry, metallurgy, fertilizer, etc.. In light woven industry, HEDP is used as detergent for metal and nonmetal. In dyeing industry, HEDP is used as peroxide stabilizer and dye-fixing agent; In non-cyanide electroplating, HEDP is used as chelating agent. The dosage of 1-10mg/L is preferred as scale inhibitor, 10-50mg/L as corrosion inhibitor, and 1000-2000mg/L as detergent. Usually, HEDP is used together with polycarboxylic acid.

Package and Storage:

HEDP 60% : 220 kg drum or 1250 kg / IBC.

Storage for one year in shady room and dry place.

hedp 60  HEDP  HEDP

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