Phosphonates H.E.D.P, also called Etidronic acid or 1-hydroxyethylidene-1,1- diphosphonic acid (HEDP) is an organophosphoric acid corrosion inhibitor that is used in detergents, water treatment, cosmetics and pharmaceutical treatment.

Hydroxyethylidene Diphosphonic acid (HEDP) shows excellent scale and corrosion inhibition effects under temperature 250℃ and good chemical stability under high pH value, hard to be hydrolysed, 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). Phosphonates (HEDP) can react with metal ions in water system to form hexa-element chelating complex, with calcium ion in particular. It is also used as deflocculent and sequestrant in cooling water treatment, boiler water treatment, industrial and institutional cleaners, swimming pool stain prevention and personal care products.