Calcium carbonate scaling is often a major problem in different aspects of industrial processes and domestic installations. The influence of metal cations on the precipitation of calcium carbonate has always attracted the attention of researchers [ ]. The techniques adopted to examine the effect of these cations are generally based on chemical and electrochemical scaling tests [ ]. The current study describes the influence of copper and zinc cations on the precipitation of CaCO3.The anti-scaling effect of these ions, in synthetic waters, was studied by using fast controlled precipitation (FCP) method [ ] and electrochemical quartz crystal microbalance (EQCM). These measurements allow to following the process of germination and growth of calcium carbonate in solution or on a metallic surface. EQCM is a high-precision instrument for measuring mass variation on the active gold surface [ ]. This technique, based on QCM with a pre-scaled detection surface (SQCM method), was used to track the scale deposition rate. The effectiveness of an anti-scale treatment results in a delay in the precipitation process. The results obtained show that Cu2+ and Zn2+ ions are very efficient scale inhibitors. In addition, it has been shown that Zn2+ ion inhibits more the scale formation than Cu2+. Indeed, with a hardness of 50° F, the optimal dose is 4 mg L-1 for Zn2+ and 5 mg L-1 for Cu2+. These results are confirmed by SQCM method. [ ]: Wen-jun L., Hui F., Lédion J., Xing-wu W., Ionics, 14, 449 (2008). [ ]: Ghizellaoui S., Lédion J., Ghizellaoui S., Chibani A., Desalination, 166, 315 (2004). [ ] : Gauthier G., Chao Y., Horner O., Alos-Ramos O., Hui F., Lédion J., Perrot H.,Desalination, 299, 89 (2012). [ ] : Dimitri P., Cheap-Charpentier H., Horner O., perrot H., water Process Engineering, 7, 11 ( 2015) Both scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis showed that these ions may affect the crystalline morphology of CaCO3. Thanks to Mrs.Francoise Pillier for FEG-SEM analysis and Mr. Cyrille Bazin for XRD characterization.