Influence of pulse current on the electrodeposition behaviors of CaCO3 scale in the industrial circulating water system

The deposition of the CaCO3 crystals in circulating cooling water is crucial to industrial water softening, which is beneficial to avoiding internal scaling and improving production efficiency. This paper focuses on the practicability of electrochemical techniques to analyze the influence of pulse current on the electrodeposition of CaCO3 in blank and high salinity conditions, including linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy tests. We assessed the coverage and compactness of the CaCO3 scale layer by obtaining residual current density (ir) and polarization resistance (Rp) values. Electrochemical results revealed that pulse electrodeposition can generate a more compact CaCO3 scale layer by Ostwald ripening, while the salt effect of NaCl can inhibit the nucleation and growth of CaCO3 crystals. Scanning electron microscope and X-ray diffractometer tests showed that unstable CaCO3 crystals can be dissolved and the size of calcites had changed with Ostwald ripening. Longer pulse-off time is beneficial to Ostwald ripening of CaCO3 crystals and nucleation in the first and second periods can influence the size of calcites formed under pulse current.