Equivalent electrical model for high current density zinc electrodeposition: Investigation through polarization curves and electrochemical impedance spectroscopy

Polarization resistance of a batch process at 2000 Am−2 of zinc electrodeposition is investigated by means of Electrochemical Impedance Spectroscopy (EIS) and polarization curves U(j). This work proposes EIS and U(j) characterisations over time with current density range from 50 Am−2 to 4000 Am−2, corresponding to a variation from [H2SO4] = 130 gL−1 and [Zn2+] = 120 gL−1 to approximately [H2SO4] = 280 gL−1 and [Zn2+] = 20 gL−1. A drift correction of EIS measurement using linear interpolation in time is provided. These measurements allow for the observation of the main physicochemical reactions occurring during the Ergosup batch process and contributing to the polarization resistance of zinc electrodeposition at high current density: charge transfer and adsorption at the cathode, charge transfer and mass transport at the anode. Simplified reaction mechanisms are used and has led to the development of an equivalent electrical model, which accounts for the various phenomena observed during the process. The equivalent electrical model is developed from the kinetic equations describing the electrochemical process. The model is able to reproduce the experimental impedance curves at high current densities with high correlation coefficients (R2> 0.9990).