1-Hydroxyethylidene-1,1-diphosphonic acid, HEDP

Product Overview

Etidronic Acid (common names HEDP, hydroxyethylidene diphosphonic acid, brand Dequest 2010) — CAS 2809-21-4 — is a water-soluble phosphonic acid used as a scale inhibitor, corrosion inhibitor and chelating agent. It forms stable chelates with calcium, iron and copper, dissolves metal oxides and retains activity under high pH and elevated temperatures (effective up to ~250 °C in formulated systems). HEDP is unusually resistant to chlorine oxidation versus many other phosphonates, making it ideal for combined-treatment programs.

HEDP is an organic phosphonic acid scale and corrosion inhibitor that can form stable complexes with various metal ions such as iron, copper, and zinc, and dissolve oxides on metal surfaces. It can still play a good role in corrosion and scale inhibition at 250 ℃, remains stable at high pH, is not easily hydrolyzed, and is generally not easily decomposed under light and heat conditions. The acid, alkali, and chlorine oxidation resistance are better than other organic phosphonic acids (salts). It can form hexagonal chelates with metal ions, especially calcium ions, in water, thus exhibiting good scale inhibition effect and significant solubility limit effect. When used in combination with other water treatment agents, it shows ideal synergistic effect.
HEDP solid belongs to high-purity products and is suitable for harsh winter regions; Specially suitable for cleaning agents and daily chemical additives in the electronics industry.

Key Grades & Typical Specs

Performance & Benefits

Scale inhibition & solubility limit effect: forms hexagonal chelates with Ca²⁺ to suppress calcium carbonate/carbonate scaling.
Corrosion control: complexes Fe/Cu/Zn oxides and contributes to corrosion inhibition in cooling water, boilers and oilfield systems.
Thermal & pH stability: maintains activity at elevated temperatures and over wide pH ranges.
Chlorine tolerance: superior resistance to chlorine oxidation compared with many organophosphonates.
Synergy: works well in multicomponent water-treatment programs (polymer dispersants, zinc salts, film-forming inhibitors).

Typical Applications

Industrial water treatment: circulating cooling water, heat exchangers, medium/low pressure boilers, RO pretreatment and desalination anti-scaling.
Oil & gas: water injection systems and pipeline scale control.
Electroplating & metal finishing: cyanide-free complexing agent and cleaner.
Textile & dyeing: peroxide stabilizer, metal chelator and cleaning agent.
Detergents & daily chemicals: chelating agent in dishwashing and soap formulations.
Cosmetics & personal care: chelator / stabilizer in some rinse-off and leave-on products (use grade-appropriate material and follow regs).

HEDP is widely used in industrial circulating cooling water systems such as power, chemical, metallurgical, and fertilizer industries, as well as for scale and corrosion inhibition in medium and low pressure boilers, oilfield water injection, and oil pipelines; In the textile industry, it can be used as a cleaning agent for metals and non metals, a peroxide stabilizer and fixing agent for the dyeing industry, a complexing agent for cyanide free electroplating industry, and a carrier for radioactive elements in the pharmaceutical industry.

Technical & Safety Notes

Handling: corrosive to metals at high concentration; wear eye/skin protection and avoid inhalation of solids. In case of contact, flush with water.
Toxicity: low acute toxicity (refer to MSDS); avoid release to untreated environment in large concentrations.
Compatibility: do not mix with strong oxidizers or strong alkalis for storage. HEDP can be part-degraded by free chlorine at sufficient residuals; design dosing accordingly.

Packaging, Supply & Commercial Info