A kinetic approach to desalinated water corrosion control by CaCO3 films

The corrosive tendency of desalinated water is usually controlled by contacting acidified water with CaCO3 particles to make it slightly supersaturated with respect to CaCO3. The desired result is to deposit on the water pipe surface a corrosion prevention film of calcium carbonate. However the considerable research efforts aiming to predict water characteristics ensuring formation of adequate protective coatings have so far yielded only rough qualitative guidelines. A major inadequacy of all available water composition criteria for ensuring the formation of adequate corrosion prevention films is that they are of thermodynamic nature while the precipitation of CaCO3 films is governed by process kinetics. The most commonly used criteria, LSI and CCPP, denote the extent of the supersaturation level with no information on the rate of deposit formation. The objective of this paper is to stress the need to extend the current approach by quantitative kinetic criteria. Induction time and CaCO3 deposition rate are essential kinetic tools for guiding the formation of adequate CaCO3 protective layers and should be integrated in regulatory specifications for re-mineralized desalinated water composition.