MORPHOLOGY SAND STRUCTURE OF CACO3 SCALE LAYERS FORMED UNDER ISOTHERMAL FLOW CONDITIONS

The morphology and the growth pattern of calcium carbonate deposits fo rmed on inner pipe surfaces, under turbulent flow, are studied. At tem peratures below 30 degrees C, and for relatively high supersaturations , quite compact calcite layers are obtained, consisting of crystals gr owing nearly perpendicularly to the substrate surface in a columnar pa ttern. For small supersaturations (i.e., below a critical value S-c si milar to 7), the deposition rate is drastically reduced and large isol ated crystals are formed. At temperatures above 30 degrees C, rather w eak dendritic aragonite patterns are dominant. The removal of magnesiu m from the tap water (used in the tests) results in the formation of a ll three polymorphs.