Calcium Phosphate Scale
Definition
Low solubility deposits formed when orthophosphate reacts with calcium, strongly favored by elevated pH and temperature.
It appears most often in phosphate treated systems, where polyphosphates hydrolyze to orthophosphate and phosphonates degrade under oxidizing or thermal stress. The released orthophosphate then reacts with calcium, especially at high pH, to form deposits. This is frustrating because the chemistry added to prevent deposition can become the source of deposition when overstressed or overfed.
Related concepts
Temperature Effect on Solubility · Polyphosphates · Phosphonates
Part of The Blueprint of Water · 🧪 chemistry