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 [1]. The techniques adopted to examine the effect of these cations are generally based on chemical and electrochemical scaling tests [2]. 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 [3] and scaling quartz crystal microbalance (SQCM). These measurements allow to following the process of germination and growth of calcium carbonate in solution or on a metallic surface. QCM is a high-precision instrument for measuring mass variation on the active gold surface [4]. 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. Both scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis showed that these ions may affect the crystalline morphology of CaCO3. References: 1. Wen-jun, L; Hui,F; Lédion, J; Xing-wu, W, Ionics, 2008, 14, 449-454. 2. Ghizellaoui, S; Lédion, J ; Ghizellaoui, S; Chibani, A, Desalination, 2004, 166, 315-327. 3. Gauthier,G ; Chao, Y; Horner, O ; Alos-Ramos, O ; Hui F., Lédion, J ; Perrot, H,Desalination, 2012, 299, 89-95. 4. Dimitri, P; Cheap-Charpentier, H; Horner, O; Perrot, H, water Process Engineering, 2015, 7, 11-20.