Main properties and applications of HEDTMP·Na5

What is HEDTMP·Na₅?

HEDTMP·Na₅ is the sodium salt of HEDTMP (1-Hydroxy Ethylidene-1,1-Diphosphonic Acid Tetrasodium Salt). It's a member of the phosphonate family of water treatment chemicals, widely valued for its excellent scale inhibition and corrosion control properties.

The "·Na₅" indicates it is typically supplied as a pentasodium salt, which gives it high water solubility and makes it easier to handle than the acidic form.

Main Properties

HEDTMP·Na₅ possesses a combination of physical and chemical properties that make it highly effective for industrial applications.

Property Category Description

Chemical Structure Contains a C-P-C bond and multiple phosphonate groups (-PO₃H₂) that are partially neutralized to sodium salts. The "Hydroxy Ethylidene" group enhances its stability.

Physical Form Typically supplied as a clear, amber to light yellow liquid or sometimes as a white crystalline powder.

Solubility Highly soluble in water. This is a key advantage, allowing for easy dosing and rapid dispersion in water systems.

Stability Excellent thermal and hydrolytic stability. It performs effectively at high temperatures (up to 200°C+ under certain conditions) and over a wide pH range without breaking down easily. This is superior to many polyphosphates.

Chelation & Threshold Effect 1. Chelation: It can form stable, water-soluble complexes with di- and trivalent metal ions (e.g., Ca²⁺, Mg²⁺, Ba²⁺, Fe³⁺).

2. Threshold Inhibition: More importantly, it works at sub-stoichiometric levels (doses lower than the stoichiometric amount of the scaling ion). It adsorbs onto the surface of microcrystals, distorting their crystal structure and preventing them from growing and depositing as scale.

Corrosion Inhibition It acts as an anodic inhibitor. By adsorbing onto the metal surface (e.g., carbon steel), it forms a protective film that blocks the anodic dissolution sites, thereby suppressing corrosion.

Synergism It exhibits a h3 synergistic effect when used with other water treatment chemicals, particularly zinc ions and polymeric dispersants. The combination provides far better corrosion and scale control than any single component alone.

Environmental Impact Phosphonates like HEDTMP are generally considered to have low to moderate toxicity and are biodegradable, though the process can be slow. They are often preferred over more persistent organic inhibitors.

Main Applications

The properties of HEDTMP·Na₅ make it a versatile workhorse in several key industries, primarily for water treatment.

1. Industrial Water Treatment (Primary Application)

This is the largest application area, specifically in recirculating cooling water systems and boiler water systems.

Scale Inhibition: Highly effective against calcium carbonate (CaCO₃) and calcium sulfate (CaSO₄) scale. It also shows good activity against barium sulfate and calcium phosphate scale.

Corrosion Control: Protects metals like carbon steel, copper, and their alloys in the water system by forming a protective film.

Stabilization: It helps to keep iron (Fe³⁺) and manganese (Mn²⁺) in solution, preventing them from depositing.

2. Oilfield Industry

Scale Squeeze Treatment: In oil and gas wells, it is injected ("squeezed") into the formation. It adsorbs onto the rock and then slowly desorbs back into the produced water, preventing scale deposition (e.g., CaCO₃, CaSO₄, BaSO₄) in the wellbore and production tubing over an extended period (weeks or months).

Perforation Fluids & Brines: Added to completion brines (like CaCl₂ or CaBr₂) to prevent precipitation of calcium carbonate or sulfate scales.

3. Detergents and Cleaning Formulations

Builder and Sequestrant: Acts as a builder in liquid detergents and cleaners by sequestering hardness ions (Ca²⁺, Mg²⁺) in the wash water. This prevents the ions from interfering with the surfactants, improving cleaning efficiency and preventing scum formation.

Stabilizer for Peroxide: Helps to stabilize hydrogen peroxide (H₂O₂) in bleach-containing formulations, preventing its rapid decomposition.

4. Textile & Pulp/Paper Processing

Peroxide Stabilizer: Used in the bleaching stages of both textiles and pulp to stabilize hydrogen peroxide, allowing for a more controlled and effective bleaching process.

Chelant: Prevents metal-ion-catalyzed decomposition of other chemicals and avoids unwanted discoloration (e.g., from iron deposits).

5. Personal Care Products

Chelating Agent: Used in shampoos, soaps, and other personal care products to complex with metal ions in hard water, which improves lather, prevents rancidity, and enhances the stability of the formulation.

Summary of Advantages

High Efficiency: Works at low dosages.

Broad-Spectrum Activity: Effective against common scales and for corrosion control.

High Stability: Resists breakdown under harsh conditions.

Synergistic: Works well in formulated products.

Water-Soluble: Easy to handle and dose.

In conclusion, HEDTMP·Na₅ is a powerful and versatile phosphonate whose key properties of excellent scale inhibition, corrosion control, and high stability underpin its widespread use across water treatment, oilfield, detergent, and process industries.