Nucleation and growth of calcium carbonate by an electrochemical scaling process

Calcium carbonate scale was electrochemically deposited from carbonically p ure hard waters on gold electrodes of an electrochemical quartz crystal mic robalance. Various data concerning the rate of the scaling process were ded uced from the chronoelectrogravimetric responses. The nucleation rate of Ca CO3 crystals and the surface coverage were evaluated from SEM image analysi s. The effects of a surface pretreatment, the oxygen concentration and the degree of hardness of the water were investigated. Transmission electron mi croscopy was used to identify the crystal structure of small nuclei. Calcit e, aragonite or vaterite crystal forms were obtained depending on experimen tal conditions. It was shown that at room temperature calcite was predomina ntly formed for conditions which were favorable to a fast nucleation rate w hereas the vaterite form is systematically obtained for experimental condit ions leading to a slow nucleation rate. The temperature increase favored th e formation of either aragonite needles or vaterite crystallites with a dif ferent morphology. (C) 1999 Published by Elsevier Science B.V. All rights r eserved.