Acrylic Terpolymers in High-Stress & Zero Liquid Discharge (ZLD) Cooling Water Systems
1. Tri-Monomer Synergy & Chemical Structure
An acrylic terpolymer incorporates three distinctly engineered functional monomers:
- Acrylic Acid (Carboxylate Group): Provides electrostatic repulsion and threshold crystal lattice distortion for calcium carbonate (CaCO₃).
- 2-Acrylamido-2-Methylpropane Sulfonic Acid (AMPS / Sulfonate Group): Introduces a strongly acidic, bulky sulfonate group that prevents calcium-polymer precipitation, providing calcium tolerance up to 3,000+ mg/L as CaCO₃.
- Non-Ionic Monomer (Ester / Polyether): Imparts steric hindrance and hydrophobic interaction to prevent silica polymerization and iron oxide agglomeration.
2. Performance in High-Phosphate & High-Alkalinity Programs
When cooling water programs use orthophosphates or polyphosphates for steel corrosion inhibition, the risk of amorphous tricalcium phosphate Ca₃(PO₄)₂ precipitation increases exponentially above pH 7.8. Standard PAA fails completely in this regime. ZEELCHEM™ 7000 maintains > 90% phosphate scale inhibition even in water containing 10–20 ppm orthophosphate and 500 ppm calcium hardness.
3. Zinc Stabilization for Alkaline Cooling Programs
Zinc salts are widely used as cathodic corrosion inhibitors. However, at cooling water pH > 8.0, zinc rapidly precipitates as insoluble zinc hydroxide Zn(OH)₂ sludge. Acrylic terpolymers effectively stabilize soluble zinc ions across pH 7.5–9.2, allowing low corrosion rates (< 1.0 mpy on mild steel).