EDTMPS is the sodium salt form of EDTMPA (Ethylene Diamine Tetra (Methylene Phosphonic Acid)). It is a widely used organophosphonate-based water treatment chemical, primarily functioning as a scale inhibitor and corrosion inhibitor.
Key Characteristics
Appearance: Light yellow to yellow-brown transparent liquid, fully miscible with water.
Chemical nature: An organophosphonate with multiple phosphonic acid groups, typically supplied as a pentasodium salt in aqueous solution.
Thermal stability: Effective as a scale inhibitor even at temperatures up to 200°C.
pH (1% solution): 9.5 – 10.5 (alkaline).
Mechanism of Action
In water, EDTMPS dissociates into multiple anionic species that can chelate metal ions such as calcium, magnesium, and barium. This interferes with the normal crystallization of scale-forming salts, making it particularly effective against calcium sulfate and barium sulfate scales.
Typical Specifications (per HG/T 3538)
Parameter Value
Active content (as EDTMPS) ≥ 28.0% or ≥ 30.0%
pH (1% aqueous solution) 9.5 – 10.5
Density (20°C) ≥ 1.25 g/cm³
Main Applications
Circulating cooling water systems: Scale and corrosion inhibition; typical dosage 2 – 10 mg/L when used alone.
Low-pressure boilers: Often blended with HPMA (hydrolyzed polymaleic anhydride) at a ratio of about 1:3.
Other uses: Complexing agent for cyanide-free electroplating, chelating agent and peroxide bleaching stabilizer in textile dyeing and finishing.
Additional Notes
EDTMPS acts as a cathodic-type corrosion inhibitor, with corrosion inhibition efficiency 3–5 times higher than inorganic polyphosphates. It has low toxicity and is relatively environmentally friendly compared to some traditional inhibitors.