7. Mineral deposits and their treatment

Scaling is a deposit that forms on exchange surfaces. Depending on the ions present in the make-up water (calcium, magnesium, sulfate, bicarbonate), those that can be added by treatments (phosphate), brought by the process (oxalate, fluoride, barium) or from corrosion (iron), we observe deposits of calcium carbonate, calcium sulfate, magnesium sulfate, tricalcium phosphate, iron phosphate, ferric hydroxide, calcium oxalate, calcium fluoride or barium sulfate (table 11 ). The solubilities of these salts are very low, and often vary with pH and temperature according to the law of mass action and the equilibria of the various species.