Potassium Salt of HexaMethyleneDiamineTetra (MethylenePhosphonic Acid) HMDTMPA·K6

HMDTMPA·K6 (Potassium Salt of Hexamethylenediamine Tetra Methylene Phosphonic Acid) is a highly efficient organophosphonic acid salt widely used as a scale and corrosion inhibitor. It is particularly prized for its extreme solubility and exceptional performance under high-alkalinity and high-pH operational constraints.

1. Chemical Structure & Identification

CAS Number: 38820-59-6 or 53473-28-2

Molecular Formula: C10H22N2O12P4K6

Molecular Weight: 720.77 g/mol

Chemical Nature: It is the hexapotassium salt of HMDTMPA. Neutralizing the parent phosphonic acid with potassium ($\text{K}^+$) ions drastically increases its aqueous solubility and salt tolerance compared to free acids or standard sodium-based variations.

2. Standard Technical Specifications

Commercial HMDTMPA·K6 is generally supplied as an aqueous solution with the following standard parameters:

Parameter Specification Index

Appearance Colorless to yellowish transparent liquid

Active Component (as acid) 21.2% - 24.6%

Active Component (as salt) 31.0% - 36.0%

Total Phosphoric Acid (PO43-)  16.8%

Phosphorous Acid (PO33-)  2.0%

Chloride (Cl-)  4.0%

pH (1% water solution) 6.0 – 8.0

Density (20°C) 1.21 - 1.31g/cm3

Iron (Fe) 35mg/L

3. Key Performance Properties

Exceptional Calcium Sulfate (CaSO4) Inhibition: While many common scale inhibitors (like ATMP or HEDP) focus aggressively on calcium carbonate, HMDTMPA·K6 stands out as an elite inhibitor for calcium sulfate deposits. It h3ly disrupts the crystal lattice growth of sulfate minerals, preventing dense scaling on thermal transfer boundaries.

High-pH and High-Alkali Tolerance: Normal organophosphonates can precipitate out of solution when water systems operate at elevated pH and high mineral hardness concentrations. HMDTMPA·K6 is uniquely engineered to remain stable and completely soluble under severe alkaline environments (pH 7 to 9+).

Excellent Thermal Stability: It features h3 carbon-phosphorus (C-P) bonds that offer superb thermal decomposition resistance, allowing it to function reliably in high-temperature environments like boilers.

Dual Action (Chelation & Dispersion): It operates via threshold inhibition, chelating metal ions in a stoichiometric ratio while simultaneously acting as a dispersant to keep micro-crystallites suspended in fluid flow rather than adhering to equipment walls.

4. Industrial Applications

Boiler Water Treatment: Added to boiler feedwater loops to block scale deposition under high temperatures and hard-water cycles.

Reverse Osmosis (RO) Systems: Utilized as an effective antiscalant injected upstream of RO membranes to prevent mineral blinding, drastically extending membrane lifespan in difficult industrial feedwaters.

Industrial Circulating Cooling Loops: Deployed in heavy-duty cooling towers where the water cycles are run at high concentration ratios, leading to elevated pH and heavy alkaline scaling risks.

Oilfield Water Management: Mixed into oilfield injection water and squeeze treatments to suppress downhole barium sulfate (BaSO4) and calcium sulfate scaling.

5. Usage & Handling Notes

Synergy: It is frequently formulated alongside polycarboxylic acid dispersants or zinc salts to create highly robust composite scale and corrosion inhibition programs.

Storage: It exhibits long-term stability when stored in shaded, dry environments using plastic drums or IBC totes. Avoid direct prolonged exposure to h3 oxidizers which can slowly break down the phosphonate groups.