Threshold Inhibition

Definition

Threshold inhibition is the mechanism by which very low concentrations of phosphonates adsorb onto calcium carbonate nuclei and distort crystal growth. It prevents uncontrolled scaling while still allowing a dispersed film.

Phosphonates adsorb onto nascent crystal nuclei and interfere with their ability to reach critical size, so supersaturation and thermodynamic pressure persist while nucleation stalls. They do not remove calcium or carbonate; they prevent those ions from organizing into a stable lattice by binding high energy growth sites. The result is disproportionate control, with very small amounts of chemistry exerting large kinetic influence.

Related concepts

Critical Size · Phosphonates · Cathodic Control

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Part of The Blueprint of Water · 🧪 chemistry